In a wavelength converter, nonlinear medium layers containing material having an increased second order susceptibility, and linear medium layers, not containing material having a nonlinear optical characteristic of the second degree, are alternatively layered. A fundamental wave (of which the angular frequency is .omega.) is incident on the multi-layered structure in a direction normal to the major surfaces of the nonlinear medium layers and the linear medium layers, thereby generating the second harmonic of the fundamental wave (of which the angular frequency is 2.omega.). The thickness of each of the linear and nonlinear medium layers is selected to be an odd-number times as long as the coherence length. The wavelength can be converted utilizing the diagonal element d.sub.ii of the second degree, nonlinear optical tensor.
An active surface-emitting harmonic generator based on a multilayer Al.sub.x Ga.sub.1-x As non linear waveguide integrated monlithically with a tunable InGaAs single quantum well laser is provided. Controlling the difference in frequency between a signal provided by the tunable laser and another input optical signal allows an output signal to be directed to any of a plurality of directions in space. Positioning detectors near the monolithic device allows spatial addressing. The controllable monolithic device may also be used to scan and thus to read data stored on holographic media.
A mode-locking device for a laser operating at a defined wavelength, has a substrate, transparent to the defined wavelength, with a front side for receiving, incident radiation and a back side. An anti-reflection coating is formed on the front side to minimize reflection loss at the defined wavelength. A quantum well structure is arranged on the back side. A high reflectance structure is arranged behind the quantum well structure in such a way that an electric field peak in the incident radiation lies coincides with that of the quantum well structure. This device offers a more reliable and less costly approach for the production of non-linear mirrors since the layers of the dielectric stack do not have to be formed by epitaxial deposition.
A monolithic crystalline material for quasi-phase-matching is described. The material includes a plurality of wafers of an odd multiple of coherence length thickness, having their faces bonded together by diffusion bonding. The wafers are oriented relative to one another to alternate their signs of nonlinear susceptibility. The invention also includes a method for producing optical radiation of a selected frequency by quasi-phase-matching, several specific methods and materials based on the discovery responsible for the invention, a generator for radiation of 60 THZ frequency of significant power, and a method of fabricating the material.
A monolithic crystalline material for quasi-phase-matching is described. The material includes a plurality of wafers of an odd multiple of coherence length thickness, having their faces bonded together by diffusion bonding. The wafers are oriented relative to one another to alternate their signs of nonlinear susceptibility. The invention also includes a method for producing optical radiation of a selected frequency by quasi-phase-matching, several specific methods and materials based on the discovery responsible for the invention, a generator for radiation of 60 THZ frequency of significant power, and a method of fabricating the material.
A non-linear optical device in which quasi-phase matching between different optical waves of differing polarizations and refractive indices increases the interaction length between the waves. The quasi-phase matching structure includes a periodic structure over which the non-linear coefficient varies with a given period, preferably the sign of the non-linear coefficient being inverted between two alternating regions. In LiNbO.sub.3, the periodic structure can be achieved by electrical poling. The required period length is increased by selecting light waves of different polarizations for the non-linear interaction such that a large portion of the dispersion between the waves of different wavelength is compensated by the birefringence of the waves of different polarization. In particular, periodic poling can quasi-phase match radiation in the range of 0.80 .mu.m to 1.2 .mu.m to generate second harmonic generation radiation in the blue and green visible spectrum.
