A Q-switching injection laser is disclosed which includes integral emitter and saturable absorber sections of the semiconductive body. In one embodiment the emitter and absorber sections are separated by an interface region implanted with ions of a type and amount to significantly increase the resistivity at the interface. Preferably, the implanted ions have energy levels spaced far enough from the conduction and valence bands of the semiconductive body such that charge carriers cannot be thermally excited between the conduction or valence bands and the energy level of the implanted ions. In another preferred embodiment, the saturable absorber section includes implanted ions of type and amount to increase the resistivity of the region, as compared to the emitter region, so as to give saturable absorber characteristic under available pumping conditions. Likewise, preferably the implanted ion is selected such that its energy levels are sufficiently separated from the valence and conduction bands so as to prevent thermal excitation from transferring charge carriers between valance and conduction bands and the energy levels of the implanted ion. In a specific embodiment, in a GaAs injection laser doped with Ge or Si, the implanted ion may be selected from the group including O, Cr and Fe.
An iron-doped indium phosphide or gallium arsenide semiconductor laser. The emiconductor material is doped when formed by uniformly distributing transition metal ions such as iron throughout the semiconductor. The concentration of the iron ions is from about 1.times.10.sup.15 to about 1.times.10.sup.18 ions per cubic centimeter, but is limited only by the solubility of iron indium phosphide or gallium arsenide. It has been determined that the greater the concentration of ions, the easier the laser emission is obtained. At liquid helium temperature, the iron-doped semiconductor laser will operate at a wavelength near 3 microns.
A two-segment contact buried heterostructure (BH) laser is pumped by a current applied to its absorber contact from a source of high impedance on the order of 100K.OMEGA. or more. The parasitic resistance between the absorber contact and the gain contact is high on the order of 10K.OMEGA.. For a given absorber (bias) current the laser exhibits a relatively wide hysteresis on the order of 1 mA or more in the light vs. gain contact current. Such a laser is highly useful as a bistable optical element. The laser is also bistable with selected pump gain and absorber currents to exhibit a wide hysteresis of voltage across the absorber contact vs. relative amounts of light which is reflected back to the laser as feedback. The laser serve both as a light source and as a detector for reading out binary information stored as light reflective spots on a medium, e.g. a video disk.
A semiconductor laser is disclosed wherein the active region has been doped with deep-level electron traps either by proton bombarding the active region or by doping with an impurity, such as oxygen, iron, or chromium. The density of traps is such that an optical absorption parameter of greater than 30 cm.sup.-1 is achieved. This laser, when combined with an ordinary photodiode, exhibits overall optical gain thereby permitting an array of optical logic circuits.
Longitudinal mode control is achieved in a heterojunction semiconductor laser (201-208) by doping the active region (203) of the laser with a deep level electron or hole trap. The trap is chosen to have a carrier capture cross section .sigma..sub.e and an optical cross section .sigma..sub.o such that the ratio of P, the average number of photons per cubic centimeter, to P.sub.s is between 0.1 and 100 where P.sub.s is equal to (N.sigma..sub.e V/.sigma..sub.o C.sub.o), N is the carrier density, V is the carrier thermal velocity, and C.sub.o is the speed of light in the material. In a specific embodiment the active region is bombarded by photons to achieve deep level electron traps in the active region.
A type II staggered alignment multiple quantum well (MQW) is integrated into a laser cavity to implement an active Q-switched device. The MQW initially absorbs and stores energy to prevent the device from lasing. In response to an applied electric field, the MQW experiences a sudden charged carrier population inversion and emits a strong, short duration pulse having a directionality conincident with that of the beam within the lasing cavity. A generalization of the invention involves optical amplification in which photon energy is first stored in a type II staggered alignment MQW, followed by the simultaneous application of an electric field and an optical beam to the MQW, such that the stored energy is released in a sudden pulse which is amplified with respect to the applied optical beam, and is co-directional with the applied beam.
