Single-frequency diode-pumped lasers for free-space communication

Thomas J. Kane; Emily A. P. Cheng; David C. Gerstenberger; Richard W. Wallace

doi:10.1117/12.18191

1 July 1990 Single-frequency diode-pumped lasers for free-space communication

Thomas J. Kane, Emily A. P. Cheng, David C. Gerstenberger, Richard W. Wallace

Proceedings Volume 1218, Free-Space Laser Communication Technologies II; (1990) https://doi.org/10.1117/12.18191
Event: OE/LASE '90, 1990, Los Angeles, CA, United States

Abstract

Laser-diode pumping of monolithic ND:YAG rings can lead to output powers of hundreds of milliwatts from a single laser. We have built several lasers with diffraction-limited single-mode output of 380 mW. These lasers can be injection—locked in a chain configuration to sum their power, while maintaining diffraction-limited, single-frequency operation. We demonstrated this chaining technique with two lasers, with a total output of 340 mW, and expect that it is practical for up to about ten lasers. Thus with lasers of 380 mW, output of 3 Watts is possible. The chaining technique, if properly engineered, results in redundancy. Monolithic, diode-pumped Nd:YAG ring lasers can provide narrow-linewidth, tunable output which is adequate for use as a local oscillator in a coherent conununication system. We build a conunercial laser which has a linewidth of about 2 kHz, a power of 5 inilliwatts, and which is tunable over a range of 30 MHz in a few microseconds. We phase—locked one of these lasers to a second, similar laser. This demonstrates that the powerful technique of heterodyne detection is possible with a diode-pumped laser used as a local oscillator. A key to the usefulness of these lasers in space communication is modulation. We have experimented with a technique for converting the cw, infrared output of these lasers into randomly pulsed, green output useful for Pulse—Position Modulation. Energy storage in an external resonant cavity permits peak green output to be much more powerful than cw infrared input. We have also begun experimentation with techniques for phase and amplitude modulating the output of these lasers. We are taking advantage of the coherence of the output in order to reduce the voltage required for conventional electro—optic modulation.

Citation Download Citation

Thomas J. Kane, Emily A. P. Cheng, David C. Gerstenberger, and Richard W. Wallace "Single-frequency diode-pumped lasers for free-space communication", Proc. SPIE 1218, Free-Space Laser Communication Technologies II, (1 July 1990); https://doi.org/10.1117/12.18191

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