Abstract

Using room-temperature parametric oscillation of a LiNbO3 crystal pumped by a Q-switched Nd:YAG laser with a simple configuration, we have realized a widely tunable coherent terahertz- (THz-) wave source in the range between 1 and 3 THz. Inasmuch as the THz wave is affected by total internal reflection at the crystal edge, we used a Si prism coupler to couple out the THz wave. We introduce an arrayed Si-prism coupler that increases the efficiency and decreases the diffraction angle. By use of the arrayed-prism coupler, there is a sixfold increase in coupling efficiency and a 40% decrease in the far-field beam diameter, compared with the use of a single-prism coupler. We discuss the negative effect of the free carriers at the Si-prism surface that is excited by the scattered pump beam, and the positive effect of cavity rotation on the unidirectional radiation of the THz wave from a Si prism.

© 2001 Optical Society of America

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References

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  1. K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
    [CrossRef]
  2. K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
    [CrossRef]
  3. J. Shikata, K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Enhancement of THz-wave output from LiNbO3 optical parametric oscillators by cryogenic cooling,” Opt. Lett. 24, 202–204 (1999).
    [CrossRef]
  4. M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
    [CrossRef]
  5. T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
    [CrossRef]
  6. T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).
  7. T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
    [CrossRef]

1999

1998

T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
[CrossRef]

1997

T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

1996

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

1994

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

1975

M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
[CrossRef]

Bevan, J. W.

T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
[CrossRef]

Chang, J. J.

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Chapin, K. R.

T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
[CrossRef]

Fleming, R. N.

M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
[CrossRef]

Ito, H.

J. Shikata, K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Enhancement of THz-wave output from LiNbO3 optical parametric oscillators by cryogenic cooling,” Opt. Lett. 24, 202–204 (1999).
[CrossRef]

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

Kawase, K.

J. Shikata, K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Enhancement of THz-wave output from LiNbO3 optical parametric oscillators by cryogenic cooling,” Opt. Lett. 24, 202–204 (1999).
[CrossRef]

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

Mann, C. M.

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Minamide, H.

T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).

Mizuno, K.

T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Nakamura, K.

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

Nozokido, T.

T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Pantell, R. H.

M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
[CrossRef]

Piestrup, M. A.

M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
[CrossRef]

Sato, M.

J. Shikata, K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Enhancement of THz-wave output from LiNbO3 optical parametric oscillators by cryogenic cooling,” Opt. Lett. 24, 202–204 (1999).
[CrossRef]

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

Shikata, J.

Suzuki, T.

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Taniuchi, T.

J. Shikata, K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Enhancement of THz-wave output from LiNbO3 optical parametric oscillators by cryogenic cooling,” Opt. Lett. 24, 202–204 (1999).
[CrossRef]

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

Walther, T.

T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
[CrossRef]

Appl. Phys. Lett.

T. Walther, K. R. Chapin, J. W. Bevan, “Comment on ‘Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition’,” Appl. Phys. Lett. 73, 3610–3611 (1998).
[CrossRef]

K. Kawase, M. Sato, T. Taniuchi, H. Ito, “Coherent tunable THz-wave generation from LiNbO3 with monolithic grating coupler,” Appl. Phys. Lett. 68, 2483–2485 (1996).
[CrossRef]

K. Kawase, M. Sato, K. Nakamura, T. Taniuchi, H. Ito, “Unidirectional radiation of widely tunable THz wave using a prism coupler under noncollinear phase matching condition,” Appl. Phys. Lett. 71, 753–755 (1997).
[CrossRef]

M. A. Piestrup, R. N. Fleming, R. H. Pantell, “Continuously tunable submillimeter wave source,” Appl. Phys. Lett. 26, 418–419 (1975).
[CrossRef]

Electron. Commun. Jp. Part 2 Electron

T. Nozokido, H. Minamide, K. Mizuno, “Modulation of submillimeter wave radiation by laser-produced free carriers in semiconductors,” Electron. Commun. Jp. Part 2 Electron 80(no.6), 1–9 (1997).

Int. J. Infrared Millim. Waves

T. Nozokido, J. J. Chang, C. M. Mann, T. Suzuki, K. Mizuno, “Optimization of a Schottky barrier diode in the submillimeter wave region,” Int. J. Infrared Millim. Waves 15, 1851–1866 (1994).
[CrossRef]

Opt. Lett.

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Figures (5)

Fig. 1
Fig. 1

TPO with a Si-prism array. The Si-prism array was introduced to increase the output and to reduce the diffraction angle of the THz wave by increasing the coupling area. An array of seven right-angle Si-prism couplers was placed on the y surface of the LiNbO3. The total base length was 8 mm × 7 = 56 mm.

Fig. 2
Fig. 2

Typical input–output characteristics of a TPO with a Si-prism array. The THz-wave output increased to greater than six times that of a single-prism coupler because of its wide base.

Fig. 3
Fig. 3

Intensity cross section of the THz wave in the horizontal direction at distance d from a single Si-prism coupler. The measured diffraction angle of the THz wave in the far field was 1.4 deg.

Fig. 4
Fig. 4

Intensity cross section of the THz wave in the horizontal direction at distance d from the Si-prism array. A comparison of the FWHM at d = 100 cm proved that the diameter of the THz wave was 40% smaller than that of a single-prism coupler.

Fig. 5
Fig. 5

Calculated radiation angle changes for two different THz coupling methods: cut exit and Si-prism coupler. The dotted and dashed curves indicate the radiation angle changes for the cut exit Δθ c and the Si-prism coupler Δθ p , respectively. The solid curve represents the actual change in THz-beam direction when observed from outside the TPO. Inasmuch as the TPO cavity can be angle tuned by rotation of the stage in the direction counter to Δθ p , the actual angle change is much smaller than Δθ p . For comparison, the changes in radiation angle are set at zero for λTHz = 200 µm.

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