A resonant cavity and a method for manufacturing the same are provided. The resonant cavity includes a first reflective surface and a second reflective surface, each of the first and second reflective surfaces providing a phase shift of a reflected electric field component of light waves oscillating along a first principal axis that differs by about π relative to a phase shift of a reflected electric field component of light waves oscillating along a second principal axis that is normal to the first principal axis. At least one of the first and second reflective surfaces having diattenuation. The first principal axis of the first reflective surface is set rotated relative to the first principal axis of the second reflective surface by about an angle α.sub.0 between an unbroken parity-time symmetric region and a broken parity-time symmetric region. As a result, spatial hole burning and dual mode operation can be eliminated.

A laser device includes: a traveling wave type resonator comprising a first mirror and a second mirror; and a laser medium disposed between the first mirror and the second mirror. The first mirror and the second mirror are disposed such that round-trip light that travels in round trips in the resonator has a focus inside the laser medium. The laser device is configured such that: excitation light incident on the resonator is superimposed on the round-trip light at the focus and narrowed to be thinner than the round-trip light, Z.sub.R×α<0.5 is satisfied, where Z.sub.R is a Rayleigh length of the excitation light and α is an absorption coefficient of the laser medium with respect to the excitation light, and a round-trip Gouy phase shift of the resonator has a value excluding 2π×n/m where m is an integer of less than 15 and n is an integer of equal to or less than m.

A converging thermal lens is transiently formed by directing a shaped pulsed light beam having at least a first wavelength to a thermo-optic material, whereby the thermo-optic material absorbs the light beam and experiences local heating in response thereto. The heating induces a refractive index profile in the thermo-optic material that temporarily forms the converging thermal lens. In some embodiments, the refractive index of the thermo-optic material has a negative temperature dependence, and the pulsed light beam is shaped to have an inverted light pattern with a maximum intensity in an outer region of the beam cross-section. Alternatively, in some embodiments, the refractive index of the thermo-optic material has a positive temperature dependence, and the pulsed light beam is shaped to have a radially-varying light pattern with a maximum intensity in a central region of the beam cross-section.

Apparatus and methods for producing ultrashort optical pulses are described. A high-power, solid-state, passively mode-locked laser can be manufactured in a compact module that can be incorporated into a portable instrument for biological or chemical analyses. The pulsed laser may produce sub-100-ps optical pulses at a repetition rate commensurate with electronic data-acquisition rates. The optical pulses may excite samples in reaction chambers of the instrument, and be used to generate a reference clock for operating signal-acquisition and signal-processing electronics of the instrument.

Systems and methods described herein provide a thermally compensated waveguide structure having a thermal index profile configured to correct thermal aberrations caused by temperature gradients in a fast axis direction and/or correct other forms of distortions in an output beam generated by the waveguide structure. The waveguide structure includes a core region, one or more cladding, and one or more heat sinks. A geometry of these portions with respect to each other can provide a cold refractive index profile such that a cold refractive index value of a portion of the core region is less than a cold refractive index value of at least one of the one or more cladding regions. Responsive to thermal compensation, the cold refractive index profile is modified, through addition of a thermal index profile, to form a hot index profile having attributes including good overlap of the fundamental mode with the gain profile and mode clean-up through gain discrimination against higher order modes.

A method and apparatus for characterizing an optical element. The optical element is part of a laser and is mounted on a translation stage to scan the optical element transverse to an intracavity laser beam. A performance characteristic of the laser is recorded as a function of position of the optical element.

A laser apparatus that can generate a high-quality laser beam is provided. The laser apparatus is provided with a laser medium and an insulation layer. The laser medium has a first surface and a second surface. Incident laser light is incident on the first surface. The second surface totally reflects the incident laser light that is incident to the second surface at an incident angle equal to or larger than a critical angle. The insulation layer covers a second area of the second surface that surrounds a first area of the second surface, the first area totally reflecting the incident laser light. The laser medium is exposed in the first area.

An acousto-optic Q switch, a resonant cavity, and a pulse laser device for improving laser device power. The acousto-optic Q switch includes: a transparent optical element configured to form a phase grating that diffracts laser; a piezoelectric transducer arranged at one end of the transparent optical element and configured to convert electrical energy into ultrasonic energy to form the phase grating in the transparent optical element; and an absorber arranged at the other end of the transparent optical element to absorb the ultrasonic energy.

A device and a method for measuring thermal load caused by excited state absorption in laser gain crystal are disclosed. Thermal focal lengths on the tangential and sagittal planes of the laser gain crystal are obtained by obtaining the threshold when the pump power is decreased, the optimal operating point, and cavity parameters of the single-frequency laser. Individual ABCD matrices of the laser gain crystal on the tangential plane and the sagittal plane are obtained based on thermal focal length. The thermal load corresponding to the threshold when the pump power is decreased, the ESA thermal load corresponding to the threshold when the pump power is decreased, and the ESA thermal load at the optimal operating point are obtained

A device and a method for measuring a thermal load caused by energy transfer upconversion in a laser gain crystal. Increasing the pump power multiple times so that the power meter obtains multiple thresholds for a single-frequency laser; obtaining an average pump threshold of the output laser; obtaining cavity parameters of the single-frequency laser; obtaining thermal focal lengths on the tangential and sagittal planes of the laser gain crystal inside the single-frequency laser; obtaining individual ABCD matrices of the laser system on the tangential and the sagittal planes; obtaining a thermal load at the threshold based on the ABCD transfer matrix of the laser gain crystal on the tangential plane, the ABCD transfer matrix of the laser gain crystal on the sagittal plane, and the average pump threshold of the laser system; obtaining a thermal load caused by ETU at threshold based on the thermal load at the threshold.