Abstract

We report on frequency doubling of high-energy, high-repetition-rate ns pulses from a cryogenically gas cooled, multi-slab Yb:YAG laser system, using a type-I phase–matched lithium triborate (LBO) crystal. Pulse energy of 4.3 J was extracted at 515 nm for a fundamental input of 5.4 J at 10 Hz (54 W), corresponding to a conversion efficiency of 77%. However, during long-term operation, a significant reduction of efficiency (more than 25%) was observed owing to the phase mismatch arising due to the temperature-dependent refractive index change in the crystal. This forced frequent angle tuning of the crystal to recover the second-harmonic generation (SHG) energy. More than a five-fold improvement in energy stability of SHG was observed when the LBO crystal was mounted in an oven, and its temperature was controlled at 27°C. Stable frequency doubling with 0.8% rms energy variation was achieved at a higher input power of 74 W when the LBO temperature was controlled at 50°C.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Long-term energy stability of a laser is an essential parameter for a facility-worthy laser system. Next-generation laser facilities will offer not only ultra-high intensity pulses, but also high pulse rate operation, enabling more rapid exploration of experimental parameter spaces and confirming the viability of practical applications. Applications include laser particle acceleration, active real time imaging, and medical therapies [13]. Ultra-high intensity femtosecond (fs) laser systems used in such facilities rely on high-energy nanosecond (ns) pump lasers operating at green wavelengths, near 500 nm, at a high pulse repetition rate (${\sim}{10}\;{\rm Hz}$), and therefore high average power [4]. These green pulses coincide with the peak in the absorption spectrum of Ti:sapphire [5] or can be used to pump optical parametric chirped pulse amplifiers (OPCPAs) [6].

Rare-earth-doped solid-state laser materials, which are at present the most efficient sources for ns high-energy pulses, operate at wavelengths near 1 µm, and thus are not suitable for pumping ultra-high intensity fs lasers. Nonlinear frequency upconversion (doubling) of such ns high-energy infrared lasers to green wavelengths is the key step in making suitable pumps for an ultra-short high-energy fs laser.

In a previous publication [7], we demonstrated a cryogenically gas cooled diode pumped solid-state laser (DPSSL) prototype amplifier system (named DiPOLE), generating pulse energies of 10.8 J, 10 ns at 10 Hz. More recently at the Central Laser Facility (CLF), we demonstrated a higher-energy DPSSL based on DiPOLE technology that produces 100 J, 10 Hz ns pulses [8] confirming the energy scalability of the technology. Further to this, type-I second harmonic generation (SHG) of the DiPOLE laser was demonstrated in potassium deuterium phosphate (DKDP), lithuim triborate (LBO), and yttrium calcium oxyborate (YCOB) [9], where LBO was found to be the most suitable and efficient conversion crystal owing to its larger temperature and angular acceptance bandwidth for the SHG process.

In this Letter, we characterise the long-term energy stability of the type–I SHG process in a LBO crystal at 5.4 J and 10 Hz operation (54 W average power) using the DiPOLE prototype amplifier system. Although, initially high conversion efficiency of 77% was observed for type-I SHG, for an input fluence of $5.5\; {\rm J/cm}^2$, the residual absorption of the LBO crystal at 1030 and 515 nm led to an increase in the crystal temperature. The temperature-dependent change in the refractive index then gave rise to a phase mismatch for the type-I SHG process resulting in a reduction in conversion efficiency over time. One approach to compensate for the thermally induced phase mismatch and recover the SHG energy is to frequently re-tune the angle of the crystal; however, this makes the system more complicated and prone to errors if an automatic setup is adopted for re-tuning.

We propose and demonstrate a simple method of controlling the temperature of the crystal to achieve long-term energy stability of the SHG process in LBO. The experimental setup used is shown in Fig. 1. The LBO crystal (Cristal Laser, France) was 30 mm in diameter and 13 mm thick, and was cut with a theta angle of 90 deg and a phi angle of 13.6 deg type-I phase matching. To minimize surface reflections, both crystal faces were coated with a dual-band anti-reflection (DBAR) coating for 1030 and 515 nm. The linear absorption of LBO at 1064 is reported as 15 ppm/cm and 20 ppm/cm at 532 [10], and similar values are expected at 1030 and 515 nm, respectively.

 figure: Fig. 1.

Fig. 1. Schematic of the experimental setup used for frequency doubling energy stability experiments. M1–M2, dichroic mirrors (HR at 515 nm, HT at 1030 nm); W1, uncoated wedge (wedge angle 30 arcmin); M4, mirror (HR at 515 nm); M5, mirror (HR at 1030 nm); BS1, beam splitter (50:50 at 515 nm); W2, W3, wedges (fused silica wedge angle 30 arcmin); Cam 1, Cam 2, CCD cameras; EM1, EM2, energy meters; BD1, BD2, beam dumps; L1 (${f} = {500}\;{\rm mm}$), L2 (${f} = {150}\;{\rm mm}$) and L3 (${f} = {100}\;{\rm mm}$), lenses. TIC, thermal imaging camera; crystal, optical mount and holder for the LBO crystal.

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The input beam size to the SHG crystal is 10 mm square. The unconverted 1030 nm beam was transmitted through M1 and reflected from M5 into a beam dump (BD1). An uncoated wedge (W1) was positioned in front of the beam dump whose front surface reflects ${\sim}{4}\%$ of the residual beam onto a calibrated energy meter EM1 (Gentec QE50LP-S-MB). The generated 515 nm beam was reflected off M1 and M2 into a second beam dump (BD2). A second wedge (W2) before the beam dump reflects ${\sim}{4}\%$ onto another calibrated energy meter EM2 (QE50LP-S-MB) to measure 515 nm energy. The leakage of the 515 nm beam through M2 is reduced in size to 3.5 mm by a Keplarian telescope (L1 & L2) with an uncoated wedge (M3) placed between the lenses to further reduce energy. The smaller beam is reflected from a 50:50 non-polarizing beam splitter (BS) and focused onto a charge-coupled device (CCD) camera (CAM 1) by lens L3 to obtain a far-field image. The beam transmitted through the BS is directed onto a second camera (CAM 2) by mirror M4 to obtain a near-field image. Colored-glass spectral filters (FEL1000) were located in front of both CCD cameras to block any residual 1030 nm. A thermal imaging camera (TIC, FLIR A655sc) is arranged to image the surface of the LBO crystal and record its temperature.

The experiment to measure long-term energy stability was conducted in two phases. In phase one, the LBO crystal was held in a thermally isolated holder with minimal thermal contact with the surroundings. There was no attempt in this case to actively cool or heat the crystal to control its temperature. In the second phase, the LBO crystal was mounted in a temperature-controlled oven that could raise the temperature to 100°C and stabilize it to $\pm \;{0.1^\circ {\rm C}}$. A spring mechanism provided good thermal contact between the cylindrical face of the crystal and the heater element, which was thermally insulated from the surroundings by a plastic cover. The flat faces of the crystal were open to ambient air. Photographs of the individual components of the oven are shown in Fig. 2. The proportional-integral-differential settings of the oven controller were not changed during the experiments reported in this Letter.

 figure: Fig. 2.

Fig. 2. Photographs of LBO crystal oven components. The photo on the left shows the spring-loaded metallic crystal holder with the crystal in place. This is placed inside the oven unit (the photo on the right). The oven is then connected to a separate temperature control unit.

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 figure: Fig. 3.

Fig. 3. Long-term energy stability of type-I SHG in LBO in a thermally isolated mount using a $1 \; {\rm cm}_2$ beam. The black line shows total energy ($515\; {\rm nm} + {\rm unconverted}$ 1030 nm), the green line shows frequency converted energy (515 nm), and the red line shows the unconverted fundamental (1030 nm). The arrows indicate the times at which the crystal angle (theta) was changed to restore the second-harmonic energy.

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The frequency conversion performance measured over a 4 h period with the LBO crystal in the thermally isolated holder, without temperature stabilization, is shown in Fig. 3. The corresponding conversion efficiency is shown in Fig. 4. The absorption induced heating effect becomes evident within 10 min of operation, leading to a reduction in green conversion. Over the first hour of the experiment, the SHG energy drop was 1.0 J with an energy stability of 7.7% rms, and the conversion efficiency falls significantly from 77% to 52% (25% drop), as the crystal temperature rises from 21.2°C to 22.7°C ($\Delta {T} = {1.5}^\circ {\rm C}$). This was compensated for by changing the angle (theta) of the crystal. This was repeated several times during the experiment, and the exact timing is indicated on the graph by the use of arrows in Fig. 3. The higher frequency modulation seen on all curves in Fig. 3 was caused by energy instability of the front end seed pulse to the DiPOLE amplifier [7], brought about by thermal instability in the water cooling circuit of the booster amplifier. The change in LBO crystal temperature over the 4 h period measured using the TIC is shown in Fig. 5.

 figure: Fig. 4.

Fig. 4. Second-harmonic conversion efficiency for LBO in a thermally isolated holder versus time. The solid (blue) curve shows the experimental data, and the dotted (red) line shows the calculated curve. The intervals are defined after which angle tuning was utilized to recover the SHG energy.

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 figure: Fig. 5.

Fig. 5. Time dependence of temperature at the center of the rear surface of the LBO crystal over a 4 h period with the crystal in a thermally isolated holder. The blue line corresponds to measured data from the TIC, and the red line represents a rolling 5000-point average fit to the measured data. The four intervals marked match those in Fig. 4, between which the crystal angle was changed. The average dT/dt over each interval was then used to calculate the change in efficiency plotted in Fig. 4.

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We calculated the loss in efficiency expected for the measured average increase in crystal temperature with time (dT/dt) for each interval by using a ${\rm sinc}_2$ functional dependence. The calculated dependence is in good agreement with the experimentally measured changes for all four intervals shown in Fig. 4.

In phase 2, the LBO crystal was placed in the temperature-controlled oven set to 27°C (the surface temperature of the crystal was observed to be 26°C), and the efficiency of the crystal was measured for over 2.5 h, as shown in Fig. 6. After 2 h of operation, the SHG energy dropped by 0.45 J (1.5% rms stability), and the corresponding conversion efficiency dropped by less than 5%; at this point, we changed the angle of the crystal to confirm that the SHG energy could be recovered. Compared to the drop in efficiency observed in the thermally isolated case (Fig. 4), this corresponds to more than a five-fold improvement in long-term stability of the SHG process in a type-I LBO crystal.

 figure: Fig. 6.

Fig. 6. Long-term energy stability of type-I SHG in LBO in an oven set to 27°C using a $1 \; {\rm cm}_2$ beam. Total input energy of 5.4 J (black line) and average power of 54 W, 515 nm energy 4.1 J (green line) and unconverted fundamental energy 1.1 J (red line).

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Figure 7 shows a near- and far-field image of the 1030 nm beam at the output of the DiPOLE amplifier, prior to propagation and beam size reduction onto the LBO crystal, measured during the phase 1 experiment. For a 750 mm focal length lens, the far-field spot diameter (1/e) was 52.1 µm in ${X}$ axis and 58.3 µm in the ${Y}$ axis; this corresponds, respectively, to 1.8 and 2.2 times the diffraction limit. Figure 8 shows corresponding near- and far-field images of the SHG signal. For a 100 mm focal length lens, the far-field spot diameter (1/e) was 44.7 µm in the ${X}$ axis and 61.8 µm in the ${Y}$ axis, corresponding to 2.0 and 2.8 times the diffraction limit, respectively. We anticipate that the 1030 nm and SHG far-field profiles could be improved by the introduction of an adaptive optics mirror in the DiPOLE amplifier system. The 1030 and 515 nm far-field images are very similar, suggesting there is no distortion introduced on the SHG beam due to the increase in the crystal temperature. The 1030 nm near-field image displays a higher intensity on the right-hand side, similar to that observed in the near field of the 515 nm beam. This is caused by an imbalance in the helium gas cooling within the prototype DiPOLE cryogenic amplifier. This has been corrected in subsequent designs of DiPOLE cooling systems.

 figure: Fig. 7.

Fig. 7. Near-field and far-field images of 1030 nm input to the crystal.

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 figure: Fig. 8.

Fig. 8. (a) Near-field (${\rm SG} = {\rm Super}$ Gaussian fit to data) and (b) far-field images and profiles for 515 nm output.

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In a separate experiment, the 1030 nm input beam was increased in size to 14 mm square, and the pulse energy was raised to 7.4 J. To demonstrate and compare long-term stability at this higher input average power (74 W), the LBO oven temperature was increased to 35°C and 50°C. Owing to the reduced input fluence at 1030 nm of $3.8\; {\rm J/cm}^2$, the maximum conversion efficiency obtained dropped to 60% (compared to 77% for the previous experiments). Figure 9 shows the long-term energy stability of the SHG process for this setup at higher input average power. For clarity, we do not show the residual unconverted 1030 nm in the figure. No optical damage was observed to the crystal or its coating when operated at these elevated temperatures.

 figure: Fig. 9.

Fig. 9. Long-term energy stability of type-I SHG in LBO in an oven set to 35°C and 50°C using a $1.4\;{\rm cm}^2$ beam. Total input energy of 7.4 J (grey and black lines) and average power of 74 W, 515 nm energy 5.0 J (green lines), 50 W average power.

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At 35°C oven temperature, a measured temperature difference of 0.5°C was recorded between the center and the edge of the LBO crystal. For a period of 2 h of operation, the SHG energy changed by 0.5 J with a stability of 1.2% rms. At 50°C, the experiment was run for a longer period of over 2.9 h and shows a further improvement in SHG energy stability with a 0.2 J and 0.8% rms variation. These both represent a significant improvement in long-term energy stability compared to the thermally isolated LBO crystal case. This gives confidence that this approach should be scalable to higher average power operation.

In summary, we have successfully demonstrated a significant improvement in second-harmonic energy stability for long-term operation at average powers approaching 100 W by elevating and controlling the temperature of the SHG crystal. This removes the requirement to have active control of the crystal angle and the need to tune this regularly to recover SHG energy due to the thermally induced phase mismatch within the crystal. In future higher-energy and average power systems, where larger aperture SHG crystals will be needed, careful design of the crystal oven will be required to ensure that the temperature gradients inside the crystal are maintained within the temperature acceptance bandwidth of the chosen crystal. With these precautions in place, we are confident that the method will enable efficient and stable frequency doubling for high-energy and average power operation of DiPOLE systems.

Funding

United Kingdom Research and Innovation (UKRI); European Union’s Horizon 2020 (739573).

Disclosures

The authors declare no conflicts of interest.

REFERENCES

1. F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996). [CrossRef]  

2. M. H. Key, Nature 316, 314 (1985). [CrossRef]  

3. M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014). [CrossRef]  

4. “Extreme Light Infrastructure (ELI) Beamlines Facility,” https://www.eli-beams.eu.

5. M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1 –2 February , 2010.

6. O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

7. S. Banerjee, K. Ertel, P. D. Mason, P. J. Phillips, M. D. Vido, J. M. Smith, J. Butcher, C. Hernandez-Gomez, R. Justin, S. Greenhalgh, and J. L. Collier, Opt. Express 23, 19542 (2015). [CrossRef]  

8. P. D. Mason, M. Divoký, K. Ertel, J. Pillar, T. J. Butcher, M. Hanus, S. Banerjee, P. J. Phillips, J. M. Smith, M. De Vido, S. Tomlinson, O. Chekhlov, W. Shaikh, S. Blake, P. Holligan, L. Antonio, C. Hernandez-Gomez, and J. L. Collier, Optica 4, 438 (2017). [CrossRef]  

9. P. Phillips, S. Banerjee, M. Fitton, T. Davenne, J. Smith, K. Ertel, P. Mason, T. Butcher, M. De Vido, J. Greenhalgh, C. Edwards, C. Hernandez-Gomez, and J. Collier, Opt. Express 24, 17 (2016). [CrossRef]  

10. “Cristal laser,” private communication and website, http://www.cristal-laser.com/UserFiles/File/brochures-techniques/lbo.pdf

References

  • View by:

  1. F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
    [Crossref]
  2. M. H. Key, Nature 316, 314 (1985).
    [Crossref]
  3. M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
    [Crossref]
  4. “Extreme Light Infrastructure (ELI) Beamlines Facility,” https://www.eli-beams.eu .
  5. M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1–2 February, 2010.
  6. O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).
  7. S. Banerjee, K. Ertel, P. D. Mason, P. J. Phillips, M. D. Vido, J. M. Smith, J. Butcher, C. Hernandez-Gomez, R. Justin, S. Greenhalgh, and J. L. Collier, Opt. Express 23, 19542 (2015).
    [Crossref]
  8. P. D. Mason, M. Divoký, K. Ertel, J. Pillar, T. J. Butcher, M. Hanus, S. Banerjee, P. J. Phillips, J. M. Smith, M. De Vido, S. Tomlinson, O. Chekhlov, W. Shaikh, S. Blake, P. Holligan, L. Antonio, C. Hernandez-Gomez, and J. L. Collier, Optica 4, 438 (2017).
    [Crossref]
  9. P. Phillips, S. Banerjee, M. Fitton, T. Davenne, J. Smith, K. Ertel, P. Mason, T. Butcher, M. De Vido, J. Greenhalgh, C. Edwards, C. Hernandez-Gomez, and J. Collier, Opt. Express 24, 17 (2016).
    [Crossref]
  10. “Cristal laser,” private communication and website, http://www.cristal-laser.com/UserFiles/File/brochures-techniques/lbo.pdf

2017 (1)

2016 (1)

2015 (1)

2014 (1)

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

1996 (1)

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

1985 (1)

M. H. Key, Nature 316, 314 (1985).
[Crossref]

Amiranoffy, F.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Antonettiz, A.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Antonio, L.

Audeberty, P.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Banerjee, S.

Bates, P.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Bernardx, D.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Blake, S.

Butcher, J.

Butcher, T.

Butcher, T. J.

Chambaret, J. P.

M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1–2 February, 2010.

Chekhlov, O.

P. D. Mason, M. Divoký, K. Ertel, J. Pillar, T. J. Butcher, M. Hanus, S. Banerjee, P. J. Phillips, J. M. Smith, M. De Vido, S. Tomlinson, O. Chekhlov, W. Shaikh, S. Blake, P. Holligan, L. Antonio, C. Hernandez-Gomez, and J. L. Collier, Optica 4, 438 (2017).
[Crossref]

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Collier, J.

Collier, J. L.

Cowan, T. E.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Crosk, B.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Danson, C. N.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Davenne, T.

De Vido, M.

Divoký, M.

Dorchiesy, F.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Edwards, C.

Enghardt, W.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Ertel, K.

Fitton, M.

Gauthiery, J. C.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Geindrey, J. P.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Greenhalgh, J.

Greenhalgh, S.

Grillonz, G.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Hancock, S.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Hanus, M.

Hernandez-Gomez, C.

Holligan, P.

Jacquetx, F.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Justin, R.

Karsch, L.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Key, M. H.

M. H. Key, Nature 316, 314 (1985).
[Crossref]

Knoll, F.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Marquésy, J. R.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Mason, P.

Mason, P. D.

Masood, M. B.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Matousek, P.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Matthieussentk, G.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Minéx, P.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

ModenaC, A.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Mora, P.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Morillo, J.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Mouliny, F.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Mouro, G.

M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1–2 February, 2010.

Najmudinc, Z.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Neely, D.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Notely, M.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Pawelke, J.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Phillips, P.

Phillips, P. J.

Pillar, J.

Ross, I. N.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Schramm, U.

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Shaikh, W.

P. D. Mason, M. Divoký, K. Ertel, J. Pillar, T. J. Butcher, M. Hanus, S. Banerjee, P. J. Phillips, J. M. Smith, M. De Vido, S. Tomlinson, O. Chekhlov, W. Shaikh, S. Blake, P. Holligan, L. Antonio, C. Hernandez-Gomez, and J. L. Collier, Optica 4, 438 (2017).
[Crossref]

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

Smith, J.

Smith, J. M.

Somekh, M.

M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1–2 February, 2010.

Speckaz, A. E.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Stenz, C.

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Tomlinson, S.

Vido, M. D.

Appl. Phys. B (1)

M. B. Masood, T. E. Cowan, W. Enghardt, L. Karsch, F. Knoll, U. Schramm, and J. Pawelke, Appl. Phys. B 117, 41 (2014).
[Crossref]

Nature (1)

M. H. Key, Nature 316, 314 (1985).
[Crossref]

Opt. Express (2)

Optica (1)

Plasma Phys. Controlled Fusion (1)

F. Amiranoffy, A. Antonettiz, P. Audeberty, D. Bernardx, B. Crosk, F. Dorchiesy, J. C. Gauthiery, J. P. Geindrey, G. Grillonz, F. Jacquetx, G. Matthieussentk, J. R. Marquésy, P. Minéx, P. Mora, A. ModenaC, J. Morillo, F. Mouliny, Z. Najmudinc, A. E. Speckaz, and C. Stenz, Plasma Phys. Controlled Fusion 38, A295 (1996).
[Crossref]

Other (4)

“Extreme Light Infrastructure (ELI) Beamlines Facility,” https://www.eli-beams.eu .

M. Somekh, J. P. Chambaret, and G. Mouro, “The APOLLON/ILE 10PW laser project,” in ELI- Nuclear Physics Meeting, Bucharest, Romania, 1–2 February, 2010.

O. Chekhlov, J. L. Collier, I. N. Ross, P. Bates, M. Notely, W. Shaikh, C. N. Danson, D. Neely, P. Matousek, and S. Hancock, “High energy broadband ultrashort pulse OPCPA system,” CLF Annual Report (2004-2005).

“Cristal laser,” private communication and website, http://www.cristal-laser.com/UserFiles/File/brochures-techniques/lbo.pdf

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Figures (9)

Fig. 1.
Fig. 1. Schematic of the experimental setup used for frequency doubling energy stability experiments. M1–M2, dichroic mirrors (HR at 515 nm, HT at 1030 nm); W1, uncoated wedge (wedge angle 30 arcmin); M4, mirror (HR at 515 nm); M5, mirror (HR at 1030 nm); BS1, beam splitter (50:50 at 515 nm); W2, W3, wedges (fused silica wedge angle 30 arcmin); Cam 1, Cam 2, CCD cameras; EM1, EM2, energy meters; BD1, BD2, beam dumps; L1 ( ${f} = {500}\;{\rm mm}$ ), L2 ( ${f} = {150}\;{\rm mm}$ ) and L3 ( ${f} = {100}\;{\rm mm}$ ), lenses. TIC, thermal imaging camera; crystal, optical mount and holder for the LBO crystal.
Fig. 2.
Fig. 2. Photographs of LBO crystal oven components. The photo on the left shows the spring-loaded metallic crystal holder with the crystal in place. This is placed inside the oven unit (the photo on the right). The oven is then connected to a separate temperature control unit.
Fig. 3.
Fig. 3. Long-term energy stability of type-I SHG in LBO in a thermally isolated mount using a $1 \; {\rm cm}_2$ beam. The black line shows total energy ( $515\; {\rm nm} + {\rm unconverted}$ 1030 nm), the green line shows frequency converted energy (515 nm), and the red line shows the unconverted fundamental (1030 nm). The arrows indicate the times at which the crystal angle (theta) was changed to restore the second-harmonic energy.
Fig. 4.
Fig. 4. Second-harmonic conversion efficiency for LBO in a thermally isolated holder versus time. The solid (blue) curve shows the experimental data, and the dotted (red) line shows the calculated curve. The intervals are defined after which angle tuning was utilized to recover the SHG energy.
Fig. 5.
Fig. 5. Time dependence of temperature at the center of the rear surface of the LBO crystal over a 4 h period with the crystal in a thermally isolated holder. The blue line corresponds to measured data from the TIC, and the red line represents a rolling 5000-point average fit to the measured data. The four intervals marked match those in Fig. 4, between which the crystal angle was changed. The average dT/dt over each interval was then used to calculate the change in efficiency plotted in Fig. 4.
Fig. 6.
Fig. 6. Long-term energy stability of type-I SHG in LBO in an oven set to 27°C using a $1 \; {\rm cm}_2$ beam. Total input energy of 5.4 J (black line) and average power of 54 W, 515 nm energy 4.1 J (green line) and unconverted fundamental energy 1.1 J (red line).
Fig. 7.
Fig. 7. Near-field and far-field images of 1030 nm input to the crystal.
Fig. 8.
Fig. 8. (a) Near-field ( ${\rm SG} = {\rm Super}$ Gaussian fit to data) and (b) far-field images and profiles for 515 nm output.
Fig. 9.
Fig. 9. Long-term energy stability of type-I SHG in LBO in an oven set to 35°C and 50°C using a $1.4\;{\rm cm}^2$ beam. Total input energy of 7.4 J (grey and black lines) and average power of 74 W, 515 nm energy 5.0 J (green lines), 50 W average power.

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