Abstract

An infrared diode laser is frequency stabilized to a tunable internally coupled Fabry-Perot interferometer (icFPI). Diode laser spectra are digitally recorded utilizing a step-by-step tuning and stabilization sequence of the icFPI. Fringes from a frequency stabilized reference He–Ne laser are used to control digital sampling steps. While improving significantly the spectral SNR, this method is combined with a confocal Fabry-Perot etalon, thus providing a frequency scale accuracy of ∼3.5 × 10−5 cm−1 over a 1-cm−1 scan. The method is shown to be consistent with high resolution Fourier transform and heterodyne spectroscopy results.

© 1989 Optical Society of America

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References

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  1. A reprint list referring to about 1000 publications concerning infrared tunable diode laser applications is available on request from the authors.
  2. P. Connes, “L'étalon de Fabry-Perot sphérique,” J. Phys. Rad. 19, 262–000 (1958).
    [CrossRef]
  3. D. E. Jennings, “Calibration of Diode Laser Spectra Using a Confocal Etalon,” Appl. Opt. 23, 1299–1301 (1984).
    [CrossRef] [PubMed]
  4. M. Reich, R. Schieder, H. J. Clar, G. Winnewisser, “Internally Coupled Fabry-Perot Interferometer for High Precision Wavelength Control of Tunable Diode Lasers,” Appl. Opt. 25, 130–135 (1986).
    [CrossRef] [PubMed]
  5. M. Reich, “Wellenlängenmessung und Stabilisierung von Dio-denlasern,” Diplomarbeit, p. 61, Ausgeführt am I. Physikalischen Institut der Universität zu Köln (1984);K. Okumura, M. Ohi, “Frequency Stabilization Under Very Small Modulation and its Stability Estimation of a PbSnTe Diode Laser,” IEEE J. Quantum Electron. QE-21, 1229–1235 (1985).
    [CrossRef]
  6. R. S. Eng, A. W. Mantz, T. R. Todd, “Low-Frequency Noise Characteristics of Pb-Salt Semiconductor Lasers,” Appl. Opt. 18, 1088–1091 (1979).
    [CrossRef] [PubMed]
  7. J. A. Silver, A. C. Stanton, “Optical Interference Fringe Reduction in Laser Absorption Experiments,” Appl. Opt. 27, 1914–1916 (1988).
    [CrossRef] [PubMed]
  8. A. Valentin, C. Nicolas, L. Henry, A. W. Mantz, “Tunable Diode Laser Control by a Stepping Michelson Interferometer,” Appl. Opt. 26, 41–46 (1987);and also C. Nicolas, “Spectrométrie de haute précision dans l'infrarouge par transformation de Fourier et par diode laser asservie en fréquence,” Thèse de Doctorat en Science, Université Paris-Sud (1985).
    [CrossRef] [PubMed]
  9. H. J. Clar, R. Schieder, M. Reich, G. Winnewisser, “High Precision Frequency Calibration of Tunable Diode Lasers Stabilized on an Internally Coupled Fabry-Perot Interferometer,” Appl. Opt. 28, 1648–1656 (1989).
    [CrossRef] [PubMed]
  10. J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
    [CrossRef]
  11. R. A. Toth, “N2O Vibration–Rotation Parameters Derived from Measurements in the 900–1090- and 1580–2380-cm−1 Regions,” J. Opt. Soc. Am. B 4, 357–374 (1987).
    [CrossRef]

1989 (1)

1988 (1)

1987 (2)

1986 (1)

1985 (1)

J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
[CrossRef]

1984 (1)

1979 (1)

1958 (1)

P. Connes, “L'étalon de Fabry-Perot sphérique,” J. Phys. Rad. 19, 262–000 (1958).
[CrossRef]

Clar, H. J.

Connes, P.

P. Connes, “L'étalon de Fabry-Perot sphérique,” J. Phys. Rad. 19, 262–000 (1958).
[CrossRef]

Eng, R. S.

Henry, L.

Hinz, A.

J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
[CrossRef]

Jennings, D. E.

Maki, A. G.

J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
[CrossRef]

Mantz, A. W.

Nicolas, C.

Reich, M.

H. J. Clar, R. Schieder, M. Reich, G. Winnewisser, “High Precision Frequency Calibration of Tunable Diode Lasers Stabilized on an Internally Coupled Fabry-Perot Interferometer,” Appl. Opt. 28, 1648–1656 (1989).
[CrossRef] [PubMed]

M. Reich, R. Schieder, H. J. Clar, G. Winnewisser, “Internally Coupled Fabry-Perot Interferometer for High Precision Wavelength Control of Tunable Diode Lasers,” Appl. Opt. 25, 130–135 (1986).
[CrossRef] [PubMed]

M. Reich, “Wellenlängenmessung und Stabilisierung von Dio-denlasern,” Diplomarbeit, p. 61, Ausgeführt am I. Physikalischen Institut der Universität zu Köln (1984);K. Okumura, M. Ohi, “Frequency Stabilization Under Very Small Modulation and its Stability Estimation of a PbSnTe Diode Laser,” IEEE J. Quantum Electron. QE-21, 1229–1235 (1985).
[CrossRef]

Schieder, R.

Silver, J. A.

Stanton, A. C.

Todd, T. R.

Toth, R. A.

Valentin, A.

Wells, J. S.

J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
[CrossRef]

Winnewisser, G.

Appl. Opt. (6)

J. Mol. Spectrosc. (1)

J. S. Wells, A. Hinz, A. G. Maki, “Heterodyne Frequency Measurements on N2O Between 1257 and 1340 cm−1,” J. Mol. Spectrosc. 114, 84–96 (1985).
[CrossRef]

J. Opt. Soc. Am. B (1)

J. Phys. Rad. (1)

P. Connes, “L'étalon de Fabry-Perot sphérique,” J. Phys. Rad. 19, 262–000 (1958).
[CrossRef]

Other (2)

A reprint list referring to about 1000 publications concerning infrared tunable diode laser applications is available on request from the authors.

M. Reich, “Wellenlängenmessung und Stabilisierung von Dio-denlasern,” Diplomarbeit, p. 61, Ausgeführt am I. Physikalischen Institut der Universität zu Köln (1984);K. Okumura, M. Ohi, “Frequency Stabilization Under Very Small Modulation and its Stability Estimation of a PbSnTe Diode Laser,” IEEE J. Quantum Electron. QE-21, 1229–1235 (1985).
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Internally coupled Fabry-Perot interferometer. The entrance and exit beams (not shown) are perpendicular to the figure plane at the beam splitter level. The rotation axis of the tuning scanner plate is also perpendicular to the figure plane. For an internal optical schematic, see Ref. 4.

Fig. 2
Fig. 2

Diode laser absorption spectra of N2O and transmission icFPI fringes recorded simultaneously. The diode laser bias current is scanned without stabilization; the scanner plate of the icFPI remains fixed. A mechanical chopper (400 Hz) modulates the IR beam and is utilized as a reference for lock-in detection.

Fig. 3
Fig. 3

Performance of the frequency stabilization: the TDL frequency is locked to an icFPI fringe, and the frequency jitter is observed on the slope of a N2O derivative absorption line. R28e of 0111 ← 0110 (2230.8561 cm−1). The time constant is 0.01 s. (A) Description of the line profile by manual tuning of the icFPI. The vertical scale in cm−1 is obtained by comparison to the quasilinear portion of the line profile. (B) Frequency jitter of the diode laser observed at P without stabilization. (C) Residual frequency jitter after stabilization to an icFPI fringe, observed at P with the same amplification as in (A) and (B). (D) Magnification 10× of (C).

Fig. 4
Fig. 4

Upper trace is a derivative spectrum of a N2O doublet (the same as presented in Fig. 2) obtained by tuning the icFPI after stabilization of the diode laser frequency to an IR fringe. The lower trace is the He–Ne laser fringe pattern associated with the icFPI tuning.

Fig. 5
Fig. 5

Second derivative absorption line of N2O recorded by coadding successive scans of frequency stabilized diode laser. The sensitivity is limited by residual optical fringes despite a noise level in the range of 10−6 absorbance units. The line is P10 of 0400 ← 0200.

Fig. 6
Fig. 6

Block diagram of the icFPI step-by-step tuning system; the computer analyzes the dc output of the lock-in amplifier and provides to the scanner driver either a stabilization error signal through the PIR or a digital ramp. The sequence triggers the IR data collection.

Fig. 7
Fig. 7

Optical diagram of the dual icFPI experiment. The frequency stabilization loop containing the tunable icFPI is located on the left side of the diagram. The frequency calibration channel containing the confocal etalon is located in the middle, and the IR spectrum channel is located on the right side of the diagram.

Fig. 8
Fig. 8

Second derivative N2O spectra corresponding to the frequency measurement of Table I and Table II. The absorption path length is 16 cm; the pressures are <1 Torr. Line assignment: *,0001 ← 0000 of 14N216O; **, 0111 ← 0110 of 14N216O.

Fig. 9
Fig. 9

First derivative N2O spectrum in the 2237-cm−1 region. The absorption path length is 16 cm, and the pressure is <1 Torr. A portion of the spectrum is expanded showing individual spectral data points. A slight background variation appears in the upper trace due to the TDL intensity variation across the scan. The third derivative line detection technique described in the text minimizes the effect of this background variation. Line assignment: *,0001 ← 0000 of 14N216O, **, 0111 ← 0110 of 14N216O, ***, 0001 ← 0000 of 14N218O, ****, 0001 ← 0000 of 14N217O.

Tables (3)

Tables Icon

Table I Average Values of Frequency Differences Taken from Four Independent N2O Spectra in the Region of 2238 cm−1

Tables Icon

Table II Frequency Differences Observed in the Regions of 2229 and 2248 cm−1 in N2O Spectrum

Tables Icon

Table III Frequency Differences Observed in the Region of 2237 cm−1 in N2O Spectrum

Equations (9)

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δ σ = σ ( δ L / L ) .
δ σ = σ × 6.328 × 10 7 .
Δ σ = 0.0016 × σ .
d σ = σ ( λ / 8 ) / L ,
d σ = σ × 3 × 10 7 ( cm 1 ) .
FS = 0.01003392 ( 5 ) cm 1
σ 2 σ 1 = ( N + n ) FS ,
d ( σ 2 σ 1 ) = d ( n ) FS + ( σ 2 σ 1 ) d ( FS ) / FS .
d ( σ 2 σ 1 ) = [ 3 × 10 5 + ( σ 2 σ 1 ) 5 × 10 6 ] ( cm 1 ) .

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