Abstract: A phasor can be employed within the resonator of an optical parametric oscillator (OPO) to adjust the absolute and relative phase of OPO beams. An embodiment of the invention comprises an OPO having at least one phasor for receiving and adjusting the phase of one or more beams resonating within the optical cavity which forms part of the OPO. Smooth alteration of the phases of the OPO beams using the at least one phasor facilitates continuous tuning of the wavelength of at least one of the beams. In another embodiment, the at least one phasor may be a translatable wedge or have adjustable refractive index to alter the phases of the OPO beams. In an additional embodiment, each at least one phasor may be comprised of more than one material, held fixedly together.

Abstract: A periodically poled second harmonic generating crystal having a long axis, said crystal comprising Magnesium Oxide doped Congruent Lithium Niobate, Magnesium Oxide doped Stoichiometric Lithium Niobate, Stoichiometric Lithium Tantalate or Potassium Titanyl Phosphate wherein the poling planes of said periodically poled crystal are canted relative to said axis and a doubled, external cavity laser utilizing said crystal, comprising an external cavity pump laser section and an extra-cavity frequency doubling section.

Abstract: Stable single mode operation of an external cavity semiconductor laser is obtained by a laser control method that monitors at least one optical beam which is generated by reflection from a wavelength selective element within the laser cavity. The method of the present invention provides stable single mode operation and significantly decreases the mode hop rate, because the signal obtained by reflection from a wavelength selective element within the laser cavity provides a clear indication of an impending mode hop.

Abstract: Improved multipass second harmonic generation (SHG) is provided by the use of an inverting, self-imaging telescope which ensures parallelism of all passes of all beams within the nonlinear medium. Improved multipass SHG is also provided by the use of a wedged phasor which provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes. Improved multipass SHG is provided by the use of an inverting self-imaging telescope in combination with a wedged phasor which provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes, ensures parallelism of all passes of all beams within the nonlinear medium. A further embodiment includes an OPO and at least one phasor and preferably first and second telescope assemblies.

Abstract: A doubled, external cavity laser comprises an external cavity pump laser section and an extra-cavity frequency doubling section. The pump laser section comprises an edge-emitting, semiconductor chip having: i) an anti-reflection coating on the chip facet facing the cavity ii) a low reflectivity coating on the output facet of the cavity, iii) a wavelength selective element on the anti-reflection side of the chip for producing a single-mode output beam, iv) at least one lens on the output side of the chip which operates to collimate the chip output beam and direct it to the frequency doubling section.

Abstract: A laser tuning mechanism which embodies “spectrally dependent spatial filtering” (SDSF) and contemplates two key elements of the tuning mechanism. The first element of the SDSF tuning mechanism is a spectrally dependent beam distortion (i.e. alteration of the amplitude and/or phase profile of the beam) provided by an SDSF tuning element in a laser cavity. The second element of the SDSF tuning mechanism is an intracavity spatial filter which makes the round trip cavity loss a sensitive function of both beam distortion and cavity alignment. Such a laser can be aligned so that a specific beam distortion, which is provided by the SDSF tuning element at a tunable wavelength, is required to obtain minimum round trip cavity loss, thereby providing tunable laser emission. A preferred embodiment of the SDSF tuning mechanism is an external cavity semiconductor laser having a zeroth order acousto-optic tuning element.

Abstract: A tunable laser and laser tuning method, based on the interaction of a spectrally dependent beam distortion and a spatial filter within a laser cavity. One embodiment of this laser is an external cavity semiconductor laser in which broad tunability is obtained by the insertion of an acousto-optic tunable filter (AOTF) into the laser cavity such that the intra-cavity laser beam passes through the AOTF in zeroth order.

Abstract: According to one embodiment of the invention, improved multipass second harmonic generation (SHG) is provided by the use of an inverting, self-imaging telescope. This embodiment ensures parallelism of all passes of all beams within the nonlinear medium. According to another embodiment of the invention, improved multipass SHG is provided by the use of a wedged phasor. This arrangement provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes. According to a further embodiment of the invention, improved multipass SHG is provided by the use of an inverting self-imaging telescope in combination with a wedged phasor. This arrangement provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes, and ensures parallelism of all passes of all beams within the nonlinear medium. This arrangement also allows corresponding passes of the pump beam and second harmonic beam to be made collinear within the nonlinear medium.

Abstract: According to one embodiment of the invention, improved multipass second harmonic generation (SHG) is provided by the use of an inverting, self-imaging telescope. This embodiment ensures parallelism of all passes of all beams within the nonlinear medium. According to another embodiment of the invention, improved multipass SHG is provided by the use of a wedged phasor. This arrangement provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes. According to a further embodiment of the invention, improved multipass SHG is provided by the use of an inverting self-imaging telescope in combination with a wedged phasor. This arrangement provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes, and ensures parallelism of all passes of all beams within the nonlinear medium. This arrangement also allows corresponding passes of the pump beam and second harmonic beam to be made collinear within the nonlinear medium.