Ona Balachninaite

Optical, vibrational, thermal, electrical, damage, and phase-matching properties of lithium thioindate

Lithium thioindate (LiInS2) is a new nonlinear chalcogenide biaxial material transparent from 0.4 to 12 μm that has been successfully grown in large sizes and with good optical quality. We report on new physical properties that are relevant for laser and nonlinear optics applications. With respect to AgGaS(e)2 ternary chalcopyrite materials, LiInS2 displays a nearly isotropic thermal expansion behavior, a 5-times-larger thermal conductivity associated with high optical damage thresholds, and an extremely low-intensity-dependent absorption, allowing direct high-power downconversion from the near-IR to the deep mid-IR. Continuous-wave difference-frequency generation (5–11 μm) of Ti:sapphire laser sources is reported for the first time to our knowledge.

Automated test station for laser-induced damage threshold measurements according to ISO 11254-2 standard

All laser components can withstand a limited intensity of optical radiation and the measurement of laser-induced damage thresholds (LIDT) is required. In the case of repetitive pulses the LIDT measurements should be performed according ISO 11254-2 standard. This procedure is time consuming and puts a high requirement on human resources. In order to speed up the LIDT measurements with a minimal human resource we developed the automated station for LIDT measurements according ISO-11254-2 standard. In this paper we overview the main parts of this automated station and present the results of LIDT measurements with repetitive pulses. In order to control the LIDT measurements, software based on LabView programming package was created. The LIDT software controls experimental sample positioning in X and Y directions, laser pulse energy attenuation and shutter. It also automates damage detection and performs statistical analysis. The program recognizes damage by detecting scattered light from damaged surface. The input of sample and laser beam technical parameters is required to start the measurements. The minimal distance between test sites on the sample surface is calculated automatically, and the surface area is divided in to a hexagonal matrix. The program also chooses the laser pulse train energy for each test site. The program also allows fast damage inspection by translating the sample under the Nomarski microscope. After completion of measurement and damage inspection, the program automatically generates the measurement report.

Characterization of the mid-infrared nonlinear crystals LiInSe2 and LiInS2 in the IR range

We report standardized absorption and scattering losses measurements of the nonlinear crystals LiInSe2 and LiInS2 in IR range by high average power 1064 nm radiation and tunable radiation of optical parametric oscillator (OPO) based on a periodically poled lithium niobate (PPLN) pumped by a diode-pumped, Q-switched TEM00 mode Nd:YVO4 laser operated at 1064 nm.

Laser conditioning of high reflectivity mirrors used in OPOs by 266 and 355 nm nanosecond pulses

Experimental investigation of the laser conditioning efficiency by nanosecond pulses at 266 and 355 nm in high reflectivity mirrors used in optical parametric oscillators (OPOs) is present in this report. The high reflection coatings were deposited on the fused silica substrates. The materials used for e-beam coating deposition were ZrO2 and SiO2. Laser conditioning was investigated as function of number of pulses, wavelength and conditioning protocol. Ramped-fluence pre-exposure was used as a method to explore optimal improvement to the damage performance at 266 and 355 nm. No conditioning effect was observed using nanosecond pulses at 266 nm, but the mirror conditioning with 355 nm pulses increased the laser-induced damage threshold (LIDT) by 2.5-3 times. The experimental results support the concept that the laser conditioning effect observed in high quality optical thin films is associated with intrinsic electronic defects in the films.

Optical characterization in wide spectral range by a coherent spectrophotometer

We report on the development and use of coherent spectrophotometers specialized for the unusual requirements of characterizing nonlinear optical materials and multilayer dielectric coatings used in laser systems. A large dynamic range is required to measure the linear properties of transmission, reflection and absorption and nonlinear properties of laser-induced damage threshold and nonlinear frequency conversion. Optical parametric oscillators generate coherent radiation that is widely tunable with instantaneous powers that can range from milliwatts to megawatts and are well matched to this application. As particular example a laser spectrophotometer based on optical parametric oscillators and a diode-pumped, Q-switched Nd:YAG laser and suitable for optical characterization in the spectral range 420-4500 nm is described. Measurements include reflectance and transmittance, absorption, scattering and laser-induced damage thresholds. Possibilities of a system based on a 130-fs Ti:sapphire laser and optical parametric generators are also discussed.

Periodically poled lithium-niobate optical parametric oscillator pumped by a diode-pumped Q-switched Nd:YAG laser

We report the optimization of a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) pumped by a diode-pumped, Q-switched Nd:YAG laser operated at 1064 nm. Total conversion efficiency exceeding 66 percent was achieved.

Optical characterization of the LiInS2 and LiInSe2 crystals

We report standardized absorption and scattering losses measurements of the nonlinear crystals LiInSe2 and LiInS2 in IR range by high average power 1064 nm radiation and tunable radiation of optical parametric oscillator (OPO) based on a periodically poled lithium niobate (PPLN) pumped by a diode-pumped, Q-switched TEM00 mode Nd:YVO4 laser operated at 1064 nm.

Absorptance and scattering losses measurements in IR range by high average power tunable radiation of optical parametric oscillator based on a periodically poled lithium niobate

We report the absorption and scattering losses measurements in IR range by high average power tunable radiation of optical parametric oscillator (OPO) based on a periodically poled lithium niobate (PPLN) pumped by a diode-pumped, Q-switched TEM00 mode Nd:YVO4 laser operated at 1064 nm.

A cherent spectrophotometer based on a periodically poled lithium niobate optical parametric oscillator for optical characterization

We report the optimisation of a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) pumped by a diode-pumped, Q-switched multiaxial TEM00 mode Nd:YAG laser operated at 1064 nm. Total conversion efficiency exceeding 66 % was achieved. This OPO is used in a coherent spectrophotometer for optical component characterisation.

A coherent spectrophotometer for optical coating chacterization

A laser spectrophotometer based on optical parametric oscillators for characterization of optical coatings in the spectral range 420 - 4500 nm is described. The characterization includes measurements of reflectance and transmittance, absorption losses, and laser-induced damage thresholds. The master oscillator of the pump-laser system is a diode-pumped, Q-switched Nd:YAG laser. Additional power, when needed for laser-induced damage threshold measurements, is obtained from flashlamp-pumped Nd:YAG amplifiers. Operation of the laser spectrometer is demonstrated by absorptance measurements and reflectance and transmission measurements of optical coatings over a wide range of angle of incidence. Damage thresholds are measured both with the OPO output and with the direct output and harmonics of the output of the amplified laser system.