Abstract
A multi-mode diode laser with an external cavity is studied experimentally and theoretically for its application to intra-cavity spectroscopy. One facet of a typical Ga0.89Al0.11As laser diode was antireflection-coated by deposition of HfO2 such that 10−3 residual reflectivity was left over. This diode was placed in an external optical cavity. The emission spectrum of this diode laser is highly sensitive to any frequency-dependent loss in the cavity, and the detectivity of such a loss grows with the pump rate. Even close to threshold, the absorption at 780 nm of Rb atoms with a density of 5×1010 cm−3 has been detected. An adequate model for diode lasers based on rate equations and including frequency-dependent gain saturation is developed and applied to the calculations of output spectra. The sensitivity of these spectra to intra-cavity absorption is determined by the overall cavity loss — which is rather high — and the fraction of spontaneous emission in the total emission, in contrast with dye lasers where it is limited by nonlinear mode coupling. Various criteria for the sensitivity are suggested. The smallest detectable absorption with a perfectly antireflection-coated laser is 10−6 cm−1. Improvement of the characteristics of the laser diode would increase the sensitivity.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
L.A. Pakhomycheva, E.A. Sviridenkov, A.F. Suchkov, L.V. Titova, S.S. Churilov: Line structure of generation spectra of lasers with inhomogeneous broadening of the amplification line. JETP Lett. 12, 43–45 (1970)
T.W. Hänsch, A.L. Schawlow, P.E. Toschek: Ultrasensitive response of a cw dye laser to selective extinction. IEEE J. QE-8, 802–804 (1972)
P.E. Toschek, V.M. Baev: One is not enough. Intracavity spectroscopy with multi-mode lasers. In Lasers, spectroscopy and new ideas, ed. by W.M. Yen, M.D. Levenson, Springer Ser. Opt. Sci., Vol. 54 (Springer, Berlin, Heidelberg 1987) pp. 89–111
G. Eisenstein, L.W. Stultz: High quality antireflection coating on laser facets by sputtered silicon nitride. Appl. Opt. 23, 161–164 (1984)
W. Rideout, R. Holmstrom, J. Lacourse, E. Meland, W. Powazinik: Ultra-low-reflectivity semiconductor optical amplifiers without antireflection coatings. Electron. Lett. 26, 36–38 (1990)
Hitachi Optodevice Data Book. Semiconductor and IC Div. Hitachi, Ltd. (1989)
K.J. Ebeling: Integrierte Optoelektronik (Springer, Berlin, Heidelberg 1989)
H.C. Casey, Jr., D.D. Sell, M.B. Panish: Refractive index of AlGaAs between 1.2 and 1.8eV. Appl. Phys. Lett. 24, 63 (1974)
G.H.B. Thompson: Physics of Semiconductor Laser Devices (Wiley, Chichester 1980)
D.R. Kaplan, P.P. Deimel: Exact calculation of the reflection coefficient for coated optical waveguide devices. AT & T Bell Syst. Tech. J. 63, 857–877 (1984)
T. Saitoh, T. Mukai, O. Mikami: Theoretical analysis and fabrication of antireflection coatings on laser diode facets. IEEE J. LT-3, 288–293 (1985)
M. Serenyi, H.-U. Habermeier: Directly controlled deposition of antireflection coatings for semiconductor lasers. Appl. Opt. 26, 845–849 (1987)
I.P. Kaminow, G. Eisenstein, L.W. Stulz: Measurement of the modal reflectivity on an antireflection coating on a superluminescent diode. IEEE J. QE-19, 493–495 (1983)
W. Demtröder: Laser Spectroscopy, Springer Ser. Chem. Phys., Vol. 5 (Springer, Berlin, Heidelberg 1988)
A.E. Siegman: Lasers (University Science Books, Mill Valley, CA 1986)
E. Kapon: Semiconductor diode laser: Theory and techniques, In Handbook of Solid-State Lasers, ed. by P.K. Cheo (Dekker, New York 1989)
O. Svelto, D.C. Hanna: Principles of Lasers (Plenum, New York 1989)
Y. Suematsu, S. Akiba, T. Hong: Measurement of spontaneous-emission factor of AlGaAs double-heterostructure semiconductor lasers. IEEE J. QE-13, 596–600 (1977)
K. Petermann; Calculated spontaneous-emission factor for double-heterostructure injection lasers with gain-induced waveguiding. IEEE J. QE-15, 566–570 (1979)
M. Port, K.J. Ebeling: Intensity noise dependence on the injection current of laser diodes with optical feedback. IEEE J. QE-26, 449–455 (1990)
K.Y. Lau, A. Yariv: A theory of longitudinal modes in semiconductor lasers. Appl. Phys. Lett. 40, 763–765 (1982)
D.T. Cassidy: Analytic description of a homogeneously broadened injection laser. IEEE J. QE-20, 913–918 (1984)
D.T. Cassidy: Comparison of rate-equation and Fabry-Perot approaches to modeling a diode laser. Appl. Opt. 22, 3321–3326 (1983)
H.C. Casey, F. Stern: Concentration-dependent absorption and spontaneous emission of heavily doped GaAs. J. Appl. Phys. 47, 631–643 (1976)
M.J. Adams, J. Buus: Two-segment cavity theory for mode selection in semiconductor lasers. IEEE J. QE-20, 99–103 (1984)
Yu.M. Aivazyan, V.M. Baev, V.V. Ivanov, S.A. Kovalenko, E.A. Sviridenkov: Kinetics of emission spectra of multimode lasers and its influence on the sensitivity of intracavity laser spectroscopy. Sov. J. Quantum Electron. 17, 168–173 (1987)
F.P. Schäfer: Dye lasers (Springer, Berlin, Heidelberg 1973) pp. 89, 93
V.M. Baev, K.-J. Boller, J. Eschner, A. Weiler, P.E. Toschek: Dynamics of a multimode dye laser after light injection. J. Opt. Soc. Am. B 7, 2181–2186 (1990)
P. Goldberg, P.W. Milonni, B. Sundaram: Theory of the fundamental laser linewidth. Phys. Rev. A 44, 1969–1985 (1991)