Coherent light generators – Particular beam control device – Producing plural wavelength output
Reexamination Certificate
1999-05-06
2001-05-22
Davie, James W. (Department: 2881)
Coherent light generators
Particular beam control device
Producing plural wavelength output
C372S050121, C372S092000, C372S099000, C372S101000, C372S102000, C372S103000
Reexamination Certificate
active
06236666
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to the field of Quantum Electronics, and more particularly to the lasers that can be widely used as a powerful tool for solving problems in optical telecommunication, information coding, interferometry, optical storage, and high resolution, low coherent and time resolved imaging spectroscopy.
Primarily, the invention can be used in cases when polychromatic laser emission with a superbroadband continuum or multiline pre-assigned spectral output is required.
II. Description of the Prior Art
The ability to generate and modulate multiple wavelengths is useful for many applications in science and engineering, e.g., in differential spectroscopy and lidar and in spectroscopic and holographic implementations of optical data storage. Recent efforts in this field has focused on design of multiple wavelength transmitters for wavelength-division multiplexed (WDM) communications systems. In particular, the multichannel grating cavity (MCG) laser or the multistripe array grating integrated cavity (MAGIC) laser have been designed and developed. In this lasers several array ridges were pumped separately to generate output at different wavelengths. However, compensation for optical cross talk can be a significant design issue for these systems as well as a lack of flexibility in the selection of wavelengths or wavelength spacing. For either schemes elaborate technology of fabrication and packaging for multistripe diode array are required.
This invention relates to an alternative design using a commercial laser diode or diode array with an external cavity. By designing this cavity structure appropriately, the system creates its own microcavities each lasing at a different wavelength within the fluorescence band of the gain medium. Mode competition in the proposed cavity is absent and spectral range of simultaneous multi-frequency generation is considerably enhanced practically to the spectral width of the active media luminescence spectrum. As a result, the radiation of each mode with its own wavelength is amplified in the active media independently from the simultaneous amplification of the rest of the wavelengths. The proposed laser transmitter is suitable for implementation at any of the major spectral bands (0.8, 1.3, and 1.5 &mgr;m) and is anticipated to be operated in a single longitudinal mode.
The proposed system is based on the principles of superbroadband oscillation—realization of simultaneous lasing in the whole spectral region of active medium amplification band. Usually competition of amplification in laser active medium restricts the spectral range of simultaneous coexistence of different wavelengths of lasing. To solve this problem it is necessary to realize independent oscillations of the certain parts of the active medium with the corresponding wavelengths.
Several authors have shown the possibility of superbroadband oscillation in the pulsed dye laser, exhibiting, unfortunately, the existence of the secondary parasitic modes in the resonator, thereby decreasing the range of a broadband oscillation. In our recent papers the first solid state superbroadband and multi-frequency laser was proposed on the basis of LiF color center crystals and lasing was realized in practically the whole amplification spectral region of LiF:F
2
−
crystals.
The prior art is represented by the following:
I. H. White, “A multichannel grating Cavity Laser for Wavelength Division Multiplexing Applications”, IEEE J. Lightwave Technology 9, 893-899 (1991).
K. R. Poguntke and J. B. D. Soole, “Design of a Multistripe Array Grating Integrated Cavity (MAGIC) Laser”, IEEE J. Lightwave Technology, 11, 2191-2200 (1993).
M. B. Danailov and I. P. Christov, “Amplification of Spatially dispersed ultrabroadband laser pulses”, Opt. Commun., 77, 397-401 (1990).
M. B. Danailov and I. P. Christov, “Ultrabroadband Laser Using Prizm-Based “Spatially-Dispersive” Resonator”, Appl., Phys. B, 51, 300-302 (1990).
T. T. Basiev, S. B. Mirov,
Room Temperature Tunable Color Center Lasers,
Laser Science and Technology books series vol. 16 pp. 1-160. Gordon and Breach Science Publishers/Harwood Academic Publishers, 1994.
T. T. Basiev, S. B. Mirov, P. G. Zverev, I. V. Kuznetsov, R. Sh. Teedeev, “Solid State Laser with Superbroadband or Control Generation Spectrum” Ser. No. 08/042,217; filed Apr. 2, 1993, US patent pending.
T. T. Basiev, P. G. Zverev, S. B. Mirov, “Superbroad-Band Laser on LiF Color Center Crystal for Near—Infrared and Visible Spectral Regions”,
Abstr. Rep. International Conf. “LASER
-93”, Munich, Germany, 1993.
T. T. Basiev, P. G. Zverev, S. B. Mirov, V. F. Federov, “Solid State Laser with Superbroadband or Control Generation Spectrum” SPIE, vol. 2379, 54-61, 1995.
T. T. Basiev, P. G. Zverev, V. V. Fedorov, S. B. Mirov, “Multline, superbroadband and sun-color oscillation of a LiF:F
2
−
color-center laser”, Applied Optics 36, 2515-2522 (1997).
SUMMARY OF THE INVENTION
The object of the present invention is to provide a semiconductor laser transmitter which is capable of lasing in multiple wavelength or superbroadband regimes of operation.
These and other objects are achieved by application of a novel external cavity for individual diode or laser diode array, wherein system creates its own microcavities each lasing at a different wavelength within the fluorescence band of the semiconductor gain medium.
According to this invention, the emission from the whole pumped volume of the diode passes through the focusing means into the aperture, which separates from the amplified emission only a part of it, that is spread parallel to the resonator axis and suppresses all the off-axis modes of radiation. The transmitted emission is retroreflected by the grating and is repeatedly directed through the gain medium through the indicated paths. As a result the radiation of every assigned wavelength is amplified without any mode competition and independently. The output radiation of the diode consists of the continuous number of beams which pass in the semiconductor crystal parallel to each other and to the laser cavity optical axis. Each of them has a certain angle incident to diffraction grating and, consequently, a distinct oscillating wavelength which is determined by a standard equation for diffraction grating working in the autocollimation regime: &lgr;=2t sin&thgr;, where “t” is the grating spacing and “&thgr;” is the incident angle. There is no interaction between these beams and it is possible to state that each part of the crystal parallel to the laser axis works as an independent laser with its own oscillating wavelength.
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Basiev Tasoltan T.
Mirov Sergey B.
Davie James W.
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
UAB Research Foundation
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