A laser cavity dumper capable of building up energy at a given mode or wavelength while emitting light of a different wavelength is created through use of a Fox interferometer with an electro-optic cell. The Fox interferometer can have either of two configurations. Placement of the electro-optic cell in either of two locations for each of these configurations will either cause the oscillating modes for the laser cavity to scan or undergo discreet shifts of preferred modes. The Fox interferometer can be adjusted for zero output of a selected wavelength under normal operating conditions. A voltage change in the electro-optic cell then changes the resonance from the lossless state through the beam-splitter causing the cavity to dump. A new mode will begin to oscillate as the previous modes are depleted.

Modulation of a semiconductor laser device is achieved at microwave frequencies by the application of transverse fields which produce energy shifts in the gain spectra of the laser device. The laser device is a PN diode which has a body portion constructed from a nonconductive material, with P and N type implants on opposite sides. The P and N implants define a transition region, or layer, on the order of 1 micron in width, in which is formed a quantum well having a thickness on the order of 50 to 100 Angstroms. Application of a bias voltage across the PN junction provides lasing of the device. An electrode on the surface of the transition layer allows application of a transverse electric field to the PN junction. This transverse field quenches the lasing of the device, to provide modulation of the laser. Quenching is produced by means of energy shifts in the gain spectra of the laser device, and since current flow through the PN junction is inhibited by the nonconductive material and thus flows primarily in the quantum wells, modulation of the current is possible at microwave frequencies at relatively low power levels.

The laser (10) has a crystal modulator (22) located at one end (16) of the laser gain medium (12) opposite the end (14) to which the total reflector or grating (18) is attached. The outcoupler (28) is spaced a predetermined nonzero distance apart from the edge (30) of the crystal (22). The spacing (d) is selected to overcome and compensate for distortions caused by thermal lensing effects in the crystal (22).

The disclosed apparatus is a temperature tracking narrow band optical range finder which includes a prior art GaAs laser diode for emitting a laser energy pulse to a target and an improved GaAs avalanche detector for receiving a reflected pulse from the target. This range finder can be arranged in a single optical axis with the laser diode electrically shielded from the detector and the reflected pulse defocused so as to impinge on the detector area surrounding the laser diode, or it can be arranged by combining the emitted and reflected pulse in an interspersed fiber optical plane.

A fiber optic communication system comprising: an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; characterized in that: the optical signal source is a laser in which frequency modulation is generated by modulating the loss of the laser cavity. A method for transmitting a signal, comprising: receiving a binary base signal having a bit period T, and generating a first signal, wherein the first signal is frequency modulated; and reshaping the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; characterized in that: the first signal is frequency modulated by using a laser in which frequency modulation is generated by modulating the loss of the laser cavity. A fiber optic communication system comprising: an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; characterized in that: the optical signal source is a laser in which frequency modulation is generated by modulating the phase of the laser cavity.