Massachusetts Institute of Technology

Emily S Kintzer

Stephen R Chinn

James N Walpole

Christine A Wang

Leo J Missaggia

James G Fujimoto

Lee J Missaggia

Vijaysekher Jayaraman

L Y Pang

A semiconductor laser oscillator structure and method is described having a tapered gain region in one-half of a laser cavity and a confocal oscillator region in another half of the cavity. An aperture is formed between two pairs of cavity spoilers located between the two cavity halves. One pair of spoilers is provided for receiving light which is reflected off of an output facet back into the semiconductor and removing it from the gain region. The other pair of spoilers removes light reflected from a curved mirror surface formed at the end of the other laser cavity half.

Tapered semiconductor laser oscillator

A semiconductor laser gain structure having a tapered gain region comprising cavity spoilers for receiving light which is reflected off of the output facet back into the semiconductor and removing it from the gain region so as to reduce or eliminate self-oscillation. The boundaries of the gain region are also designed to have a very low refractive index gradient so as to minimize reflection of light off of the boundaries back into the gain region. The gain structure may be embodied in a semiconductor laser oscillator or semiconductor laser amplifier depending on whether the input facet is or is not, respectively, anti-reflection coated. The output facet is anti-reflection coated in either embodiment.

Tapered semiconductor laser gain structure with cavity spoiling grooves

A semiconductor laser gain structure having a tapered gain region comprising cavity spoilers for receiving light which is reflected off of the output facet back into the semiconductor and removing it from the gain region so as to reduce or eliminate self oscillation. The boundaries of the gain region are also designed to have a very low refractive index gradient so as to minimize reflection of light off of the boundaries back into the gain region. The gain structure may be embodied in a semiconductor laser oscillator or semiconductor laser amplifier depending on whether the input facet is or is not, respectively, anti reflection coated. The output facet is anti-reflection coated in either embodiment.

A fast rise time optical pulse generator is provided which utilizes a laser cavity having a gain medium with a pair of cavity arms extending therefrom, each cavity arm having a feedback element at its distal end. The gain medium has the property that if optical waves enter the gain medium from the two arms simultaneously, the gain is reduced. This will generally occur as a result of a gain saturation effect such as spatial hole burning. Since the gain reduction does not occur for pulses of a length equal to the length of the laser cavity or for odd submultiples of such pulses, outputs are obtained at one of these pulse lengths. Various means are provided for tuning the system to the desire harmonic.

Optical pulse generator

In the laser diode calibration scheme disclosed herein, a glow discharge device ie employed which has an optogalvanic response wavelength within the wavelength tuning range of the laser diode. By measuring the proportion of laser diode light output which passes through an interference filter having a known wavelength dependent response, an initial operating region is determined which is at least proximate the optogalvanic response wavelength. By varying the current through or temperature of the diode within the operating region while measuring the optogalvanic response, an operating point corresponding to the response wavelength is determined. While modulating the laser diode at the data rate and at different modulation amplitudes across a response peak provided by Fabry-Perot interferometer, the relative amplitudes of sidebands generated by the interferometer are measured and compared thereby to determine a modulation amplitude providing a deviation which is a predetermined multiple of the data rate.

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Arlington, MA, United States of America

Emily S Kintzer