Massachusetts Institute of Technology

Peter A Schulz

James G Fujimoto

Tso Yee Fan

James Gregory Goodberlet

Scott Henion

Paula J Donovan

Jyhpyng Wang

Described are an optical transmitter and a method for generating a single sideband optical signal. The method includes generating a data signal at a first power level and at a second power level with a predetermined ratio being defined between the power levels. The data signal at the first power level is applied to a phase module disposed in a laser cavity of a semiconductor laser to generate a frequency modulated laser signal having a double sideband. The intensity of the frequency modulated laser signal is modulated in response to the data signal at the second power level to yield the single sideband optical signal. Optical transmitters implementing the method have an increased manufacturing yield and reliability, a lower fabrication cost and a decreased size compared to other optical single sideband optical transmitters.

Single sideband optical transmitter

A system for producing laser output from a solid-state laser is described. The laser output comprises two orthogonally polarized axial modes of light at different frequencies having linear polarization. In one embodiment, the two modes are at different frequencies and can be merged together to produce energy waves of variable frequency. This device has applications in microwave generation and velocity measurements.

Two-axial-mode solid-state laser

An optical frequency discriminator having enhanced linearity is provided, which discriminator may be utilized in FM communications systems or in other applications. The discriminator has two interferometers with the optical path length difference for the first interferometer being .DELTA.L and for the second interferometer being m.DELTA.L where m&gt;1. The optical FM signal is applied in parallel to both optical interferometers with approximately m.sup.3 times as much of the signal being applied to the first interferometer as to the second interferometer. Each interferometer has an output signal versus frequency characteristic with a substantially linear region about a center frequency, which center frequency is approximately equal to the center frequency of the input optical signal. The outputs from the interferometers are combined in a manner such as the difference in absolute value of the linear region characteristic slopes is obtained, the resulting output being a discriminated output which is substantially linear over an enhanced FM range.

Optical frequency discriminator using two mach-zehnder interferometer

A method of manufacturing a Faraday isolator which is wavelength-independent over an extended predetermined range of wavelengths and provides high isolation over the extended wavelength range.

Broadband Faraday isolator

This invention relates to a tunable solid-state laser which generates ultrashort output pulses with continuous wave pumping. The device includes a lasing medium having a gain cross section of 10.sup.-18 cm.sup.2 or less and mode beating characteristics, which lasing medium is mounted in a laser cavity. A continuous wave pumping beam is applied to the lasing medium causing an output, a portion of which is applied to an intensity dependent nonlinear cavity. The output applied to the nonlinear cavity is retroreflected back through the cavity and is interferometrically combined with the laser output. The relative lengths of the cavities are initially selected such that phase changes caused by the nonlinear medium result in substantially maximum enhancement of intensity peaks of the laser output, causing self starting of pulsed operation. Once pulsed operation is achieved, the cavity lengths may be adjusted to optimize interferometric addition of peak outputs and interferometric cancellation of pulse wings, resulting in a laser output formed of ultrashort pulses. For preferred embodiments, the laser is a titanium sapphire laser, and the nonlinear cavity contains a single mode optical fiber which induces intensity dependent phase changes in an optical signal passing therethrough. A feedback circuit is preferably provided to stabilize pulse operation.

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North Andover, MA, United States of America

Peter A Schulz