Abstract: An optical resonator has an axial mode frequency tuning rate with respect to temperature matching the peak gain frequency tuning rate, so that mode hops are eliminated. The resonator contains a composite cavity consisting of a gain medium and free space. Preferably, the resonator is a single-frequency solid state laser containing a solid state gain medium defining a physical path length Lg. The optical cavity is defined by a high reflector and output coupler surrounding the gain medium and defining a physical cavity path length Lo. The high reflector and output coupler are mounted on a substrate so that Lo is temperature insensitive. Preferably, the substrate is a thermally insensitive material having a negligible coefficient of thermal expansion; for example, it may be Invar™, Super-Invar™, ULE™ Glass, Zerodur™, and fused silica. Alternately, the substrate is a thermally isolated material that is temperature controlled and insulated from the gain medium.

Abstract: An apparatus and a method for separating a light of a first wavelength &lgr;1 from a second wavelength &lgr;2, where &lgr;1<&lgr;2, in a waveguide such as an optical fiber is described. The apparatus includes a core surrounded by a depressed cladding, which itself is surrounded by a secondary cladding. The core cross-section, the depressed cladding cross-section, the secondary cladding cross-section, and the refractive indices of the core, the depressed cladding and the secondary cladding are selected to produce a fundamental mode cutoff wavelength &lgr;c such that &lgr;1&lgr;c<&lgr;2, and produce a high loss at the secondary wavelength &lgr;2. The apparatus can be used as a filter, an amplifier, a laser, or in a nonlinear optical switch.

Abstract: A light source employing a passively Q-switched laser, a fiber amplifier and a nonlinear element for performing single pass frequency conversion to generate a pulsed output beam. The Q-switched laser delivers a pulsed primary beam at a primary wavelength which is amplified by fiber amplifier to produce a pulsed intermediate beam containing pulses at the primary wavelength. The Q-switched laser is configured such that these pulses have a certain format. Specifically, these pulses have a format corresponding to a certain frequency conversion efficiency, preferably higher than 10% or even higher than about 50% in single pass frequency conversion performed by the nonlinear element. The nonlinear element includes one or more nonlinear crystals for performing a single or cascaded nonlinear conversion operations. Depending on the application of the light source, the primary wavelength range can be chosen between 860 nm and 1100 nm and the output wavelength can range from 430 nm to 550 nm.

Abstract: A system employing a solid state light source for writing Bragg gratings in fibers and for other photolithographic applications. The solid state light source preferably has a passively Q-switched laser, a fiber amplifier and two or more nonlinear conversion elements for delivering a pulsed exposure beam at an exposure wavelength in the UV wavelength range. The exposure beam is generated in a single pass through the nonlinear elements, for example by cascaded second harmonic generation yielding the fourth harmonic. The system is effective at covering the UV wavelengths from 200 nm to 330 nm and particularly effective at producing an exposure wavelength between 240 and 250 nm at average power levels of 500 milliWatts and more within a photosensitive range of fiber cores in which Bragg gratings are to be written.

Abstract: A tunable light source equipped with an optical parametric amplifier (OPA) placed in a cavity for performing an optical parametric oscillation (OPO) driven by a pump beam at a pump frequency selected within a certain range such that the OPO is driven near degeneracy. An adjustment mechanism adjusts the pump frequency within a wavelength tuning range to select a gain spectrum of the OPO and a spectral control mechanism sets a resonant frequency of the cavity within that gain spectrum. Thus, only one of the idler and signal beams within the passband set by the narrowband tuner is supported inside the cavity. Other nonlinear frequency conversion operations can also be performed within the cavity in conjunction with the OPO. The light source can be operated in cw, near-cw and pulsed operation modes as a broadly tunable narrowband source covering a wavelength window of 250 nm.

Abstract: A method for tuning nonlinear optical frequency converters including devices such as optical parametric amplifiers and optical parametric oscillators through degeneracy. The nonlinear conversion process is driven by a pump beam at an original pump wavelength and the tuning is accomplished by setting a passband around a first wavelength generated by the optical frequency converter and thereby generating a passband image around a second wavelength. Once the passband and passband image are within a critical range the original pump wavelength is adjusted to an adjusted pump wavelength and tuning continues by moving the passband which the adjusted pump wavelength is either held constant or further adjusted. In particular, the passband can now be moved through the resonant wavelength which corresponds to a point of degeneracy at the original pump wavelength.

Abstract: An apparatus and a method for separating a light of a first wavelength &lgr;1 from a second wavelength &lgr;2, where &lgr;1<&lgr;2, in a waveguide such as an optical fiber is described. The apparatus includes a core surrounded by a depressed cladding, which itself is surrounded by a secondary cladding. The core cross-section, the depressed cladding cross-section, the secondary cladding cross-section, and the refractive indices of the core, the depressed cladding and the secondary cladding are selected to produce a fundamental mode cutoff wavelength &lgr;c such that &lgr;1&lgr;c<&lgr;2, and produce a high loss at the secondary wavelength &lgr;2. The apparatus can be used as a filter, an amplifier, a laser, or in a nonlinear optical switch.

Abstract: A pump resonant optical parametric oscillator (PROPO) is optimized for noise suppression of pump radiation of wavelength &lgr;p. The PROPO generally comprises a parametric amplifier disposed within a resonant cavity having input and output couplers. The parametric amplifier has a gain G that increases with increasing power at a pump wavelength &lgr;p. The cavity resonates at both pump wavelength &lgr;p and signal wavelength &lgr;s. The parametric amplifier transfers noise on the pump radiation to the signal radiation. Input coupler transmission TIC, output coupler pump transmission TP, signal transmission TS, and gain G are chosen such that a resonated pump power at &lgr;p is nearly clamped at a threshold level. By setting these parameters such that the PROPO has a threshold slightly lower than the available power at a wavelength of the optical pump, noise on the pump radiation may be reduced by greater than about a factor of 10.

Abstract: A chirped pulse amplification system employs chirped quasi-phase-matched (QPM) gratings as dispersive delay lines for stretching and/or compressing ultrashort pulses. QPM gratings with periods varying along the beam propagation direction produce simultaneous second-harmonic generation and, in general, both amplitude and phase modulation of this second harmonic output. The aperiodic QPM gratings are designed to provide stretching or compression of the output second harmonic pulse with respect to the fundamental-wavelength input pulse. The chirped QPM gratings are also used for simultaneous harmonic generation and compressing of the chirped output from a femtosecond laser oscillator. In general, the aperiodic QPM gratings can be used to efficiently produce arbitrarily shaped second-harmonic pulses.

Abstract: An apparatus and method for simultaneous chirp adjustment and frequency conversion of an ultra-short input optical pulse A.sub.1 characterized by a center angular frequency .omega..sub.1,0 in a non-linear optical material with a quasi-phasematching (QPM) grating exhibiting an aperiodic pattern of regions D.sub.j constituting a grating. Passing the ultra-short input optical pulse A.sub.1 through the grating gives rise to a chirp-adjusted and frequency-converted output optical pulse A.sub.2. In the preferred embodiment the non-linear optical material is a Second Harmonic Generator (SHG) such that the output optical pulse A.sub.2 generated from the input optical pulse A.sub.1 is a chirp-adjusted second harmonic of said ultra-short input optical pulse A.sub.1. In the general case the method and apparatus use a transfer function D(.OMEGA.) derived from the equation:A.sub.2 (.OMEGA.)=D(.OMEGA.).multidot.A.sub.1.sup.2 (.OMEGA.),where A.sub.1.sup.2 (.OMEGA.