This work presents concept and scaling considerations for a solid-state laser with a gain medium disk operating in the active mirror mode. The disk is of composite construction formed by bonding undoped optical medium to the peripheral edges of a gain medium disk. Pump diode arrays are placed around the perimeter of the composite disk and pump light is injected into the undoped edge. With proper choice of lasant doping, diode placement and diode divergence, a uniform laser gain can be achieved across large portions of the disk. To mitigate thermal deformations, the gain medium disk is pressure-clamped to a rigid, cooled substrate. Effective reduction of thermo-optical distortions makes this laser suitable for operation at high-average power.

We report a diode pumped 2μm Tm:YAG laser operating in a pulsed mode, with an RTP Pockels cell as the Q-switch generator. A maximum output of 2.4mJ with a pulse width of 57ns was achieved. The crystal was pumped with an input energy of 85mJ at a rate of 20Hz. To the best of our knowledge, this is the first time that RTP was used as the Q-switch generator in a 2μm laser resonator.

The dynamics of a solid-state laser sustaining the oscillation of the Laguerre-Gaussian TEM mode is experimentally studied. The results are given of investigations of the existence conditions of self- modulation, chaotic, frequency locking, and self-pulsing regimes. From the observations of the locking phenomena of the first order family occurs as a subcritical bifurcation in a solid-state laser.

We have developed a solid-state laser operating at 532nm for underwater topographic investigations. The laser system is integrated into a torpedo-like 'towed-body', with the military designation of AQS-20. This laser, along with other sophisticated receiver opto-electronic systems enables detailed underwater bathymetry. CEO designed and manufactured the laser portion of this system. The laser sub-system is comprised of two separate parts: the LTU (Laser Transmitter Unit) and the LEU (Laser Electronics Unit). The LTU and LEU where put through Mil-standard testing for vibration, shock and temperature storage and operation extremes as well as Mil-461C EMI/EMC testing. The Nd:YAG laser operates at a 400 Hz pulse repetition frequency and is controlled remotely, tethered to the system controller in a ship or helicopter. Power monitor circuits allow real time laser health monitoring, which enables input parameter adjustments for consistent laser behavior. The towed body moves forward at a constant rate of speed while this underwater LIDAR system gathers data. All heat generated must be conducted into the outer hull of the towed-body and then, to the surrounding ambient ocean water. The water temperature may vary from 0-35 degrees C.

We have investigated a simple scheme based on the combination of two intra-cavity non-linear processes, stimulated Raman scattering (SRS) in Ba(NO3)2 and second harmonic generation (SHG) in Lithium tri-borate (LBO), which efficiently convert the 1064nm fundamental of a Nd:YVO4 laser to produce orange light at 598nm. Average power up to 5mW has been generated at 598nm, for a 1.6W diode laser pump.

This paper describes the development and performance of an optical parametric oscillator based on KTP crystal and pumped by a flashlamp-pumped Q-switched Nd:YAG laser at 1.064 micrometers . The effect of an optical resonator configuration on OPO performance has been investigated experimentally. A comparison between plane-parallel, stable and unstable resonators in both energy conversion and output beam divergence was also performed and the results are discussed. In summary, we have demonstrated a compact low threshold source for the near IR in a configuration of an intracavity optical parametric oscillator based on the noncritically phase-matched KTP crystal placed inside the resonator of a multi-transverse-mode Nd:YAG laser. The 1.57 micrometers output energy of 40 mJ was achieved with a stable, short cavity KTP OPO. The overall efficiency of 0.55 percent was obtained from operating approximately 2 times above oscillation threshold. The dependence of output pulse energy on flashlamp input energy was not changed within the range of 5-50 Hz.

We report a diode pumped 2 micrometers Tm:YAG laser operating in a pulsed mode, with an RTP Pockels cell as the Q-switch generator. A maximum output of 2.4 mJ with a pulse width of 57ns was achieved. The crystal was pumped with an input energy of 85mJ at a rate of 20Hz. To the best of our knowledge, this is the first time that RTP was used as the Q-switch generator in a 2 micrometers laser resonator.

A compact high pulse energy Ti:Sapphire laser with its third harmonic has been developed for airborne ozone differential absorption lidar to study the distribution and concentration of ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a commercial frequency-doubled Nd:YAG laser with a pulse repetition frequency of 20 Hz is seeded by a single mode 900 nm diode laser. More than 130 mJ/pulse was achieved at the fundamental wavelength of 900 nm. Two nonlinear, Lithium Triborate crystals were used for the Third Harmonic Generation resulting in output pulse energy of more than 39mJ at 300nm, which is used as the off-line wavelength of an airborne ozone DIAL system. The energy conversion efficiency from 900 nm to 300 nm was 30 percent as compared to the theoretical value of 36 percent.

We established a new diode array pumped Er:Yb:Glass test setup for evaluation of the laser performance and q-switch characteristics of various saturable absorber materials at 1.54um. Pumping distribution and maximum gain was analyzed. Passive q-switched laser operation was demonstrated with both U²⁺:CaF₂ and Co²⁺:MgAl2O4. TEMoo Q-switch pulses with energy of 0.5mJ and pulse width of 10ns was obtained.

This work describes the development and characterization of a continuous-wave (cw) room-temperature intracavity-doubled Cr⁴⁺:forsterite laser which produces broadly tunable red radiation. Such a source is potentially important in spectroscopy, display technologies, and medical applications. In the experiments, a 2-cm-long Cr⁴⁺:forsterite crystal was placed in an astigmatically compensated x-cavity which was end-pumped by a 1064-nm Nd:YAG laser. The crystal which had a small-signal pump absorption of 68 percent was maintained at 20 degrees C. An intracavity Brewster-cut SF10 prism was used to tune the output of the laser. Intracavity frequency doubling was achieved by using a periodically poled lithium niobate (PPLN) crystal which had 8 different poling periods. The PPLN crystal was placed inside the resonator between a curved folding mirror and the curved output coupler. The transmission of the output coupler was 2.6 percent at 1260 nm. The PPLN temperature was maintained at 188 degrees C. By translating the PPLN crystal through sections with different poling periods, second harmonic generation was obtained in the wavelength region between 613 and 655 nm. With an incident pump power of 6.8 W at 1064 nm, the Cr⁴⁺:forsterite laser produced 245 mW of cw output power at 1260 nm and intracavity frequency doubling yielded 45 mW at 630 nm.

Detailed study of Stimulated Raman scattering (SRS) of 1.06- micrometers , 50-ps pulses in BaWO₄ and KGW crystals was performed. Single-pass, double-pass and Raman cavity arrangements were compared regarding threshold intensity, conversion efficiency and pulse structure. Single-pass conversion efficiencies reached 25 percent for both BaWO₄ and KGW. Double passing of the pump beam slightly improved the efficiency to 35 percent. Placing the BaWO₄ crystal into a cavity and optimizing the performance by varying the output coupler spectral characteristics and the resonator length, 55 percent pump-to-first-Stokes efficiency has been obtained. The maximum of the Raman laser output energy was 3 mJ. The output consisted of 2-4 picosecond pulses at the 1180 nm wavelength. Dependence of the BaWO₄ Raman laser output beam structure on the pumping energy was studied. The concentric ring profile, typical for transient SRS, was homogenized using a cyclic olefin polymer coated silver hollow glass waveguide. A similar study was performed with KGW crystal, for which the first Stokes wavelengths are 1159 nm or 1177 nm, depending on the sample orientation. Due to lower gain value, Raman laser energy reached 2 mJ and maximum efficiency was 30 percent. Based on our comparative study, a new BaWO₄ crystal is highly suitable for utilization in the near IR picosecond Raman lasers.

A compact Nd:YAP solid-state oscillator/amplifier laser system with a possibility of fast wavelength switching from 1.34 micrometers to 1.08 micrometers and with a reliable flexible radiation transport device was developed. The laser oscillator was composed of two rear mirrors, inner for 1.34 micrometers and outer for 1.08 micrometers generation. An output resonator mirror was common to both wavelengths. A crystal of V³⁺:YAG was used as a passive mode-locker at 1.34 micrometers Nd:YAP laser transition, and BDN II foil served as a saturable absorber at 1.08 micrometers laser wavelength. Both resonators were separated by a mechanical shutter. A single flashlamp oscillator-amplifier cavity configuration was utilized in order to keep the device compact and small in dimensions. At the output, either a train of 1 nsec long 1.3 micrometers pulses with the energy up to 30 mJ, or 20 nsec long 1.08 micrometers giant pulses with the energy up to 100 mJ were generated. A cyclic olefin polymer-coated silver hollow glass waveguide with the optimal coupler was used for the radiation delivery. The measured transmission for 1m long waveguide reached 93 percent and 80 percent for 1.34 micrometers and 1.08 micrometers , respectively. This alternative double- wavelength system can be suitable for medical or industrial applications.

Thinking about the pumping and generated power of the longitudinally diode-pumped solid-state laser enhancement, the question of an active material cooling should be solved. One of the possible solutions is the active material cooling surface enlargement. Besides the cylindrical surface of the crystal, the laser rod front surfaces could be cooled through undoped ends. The temperature gradient effect in three various samples was investigated in a computer experiment, and the differences in generated output power were measured experimentally. The samples were three Nd:YAG rods - one conventional, one with one undoped end, and one with two undoped ends. The crystal samples were placed in sequence into a resonator 6 cm long and longitudinally diode-pumped. The dependencies of the generated power on the absorbed pump power have shown that with the two undoped ends the output power is more than twice as high as against the conventional Nd:YAG sample. The results were explained by a computer experiment based on the heat transfer equation solution where the changes of the temperature gradient were least for the Nd:YAG rod with two undoped ends.

The analysis of tuning characteristics for parametric amplification in KD*P has shown that the application of KD*P crystals may considerably enhance the possibilities of certain optical parametric amplifiers of both terawatt and petawatt level. For instance, at pumping with a wavelength of (lambda) ₃ equals 0.527 micrometers , which is most promising for the creation of such systems, the KD*P-based amplifiers may work far from the degenerate mode, e.g., at (lambda) _s- 0.911 micrometers and (lambda) _i-1.25 micrometers . For operation at these wavelengths there are currently master oscillator of femtosecond pulses with pulse duration of up to 30 fs. In this paper elements of the system are discussed, and their parameters are optimized.

For precise design and optimization of the Q-switch solid-state laser system parameters, the computer dynamic model is useful. In the past, this problem was many times solved. Nevertheless, in most cases, as a time starting point of the rate equation, the moment of Q-switch opening was taken for the simulation. Therefore many initial parameters had to be estimated. To have a more complex view on the giant pulse generation, the initial point of a calculation must be derived in the moment of a flashlamp trigger. In our scheme, the designed system of four main differential rate equations describes the energy transfer from the pumping source - a capacitor to the output giant pulse. Designed model was used for the alexandrite active medium. The alexandrite laser system was Q-switched electro-optically and four differential equations gave the computer results. On the base of the computer and physical experiment, it can be summarized that the realistic model of the giant pulse solid-state laser was completed. This model could be simply implemented for other flashlamp solid-state laser systems.

A diode-pumped microchip laser is developed and achieves self Q-switched operation, which produces nanosecond pulses at a wavelength of 946 nm. The laser medium is a crystal of yttrium aluminum garnet (YAG) doped with both neodymium and chromium. The two surfaces of the NdCr:YAG crystal are coated with dielectric layers, which serve as the mirrors of the laser cavity. The Nd³⁺ ions in the NdCr:YAG crystal function as the gain medium while the Cr⁴⁺ ions act as a saturable absorber. The presence of the saturable absorber leads to self Q-switching, which produces laser pulses of 3.7-ns duration and 946-nm wavelength at a peak power of 240 W. When the laser output is focused onto a KNbO₃ crystal, nanosecond pulses of blue color at 473 nm are obtained. The blue laser output has a single frequency and TEM00 transverse mode at a peak power of approximately 18 W.

We report on a systematic study of the laser threshold and slope efficiency of solid-state dyes lasers operating in the near-IR under microsecond(s) pumping. The excitation source for this work is a flashlamp-pumped dye laser operating at a wavelength of approximately equal to 660 nm with a pulse duration of approximately equal to 1.25 microsecond(s) . A major objective of this work is to demonstrate laser characteristics traceable to direct diode-pumping of a dye- doped solid matrix. Detailed measurements were made for three laser dyes and three different host materials. Dyes evaluated include Rhodamine 700, Rhodamine 800 and Oxazine 725 at various concentrations. The host matrices studied were modified PMMA, polymer-filled nanoporous glass, and organically modified silicate. Laser measurements included output energy and wavelength as functions of input energy and resonator feedback. Findlay-Clay analyses were performed to extract information on the round-trip cavity losses in each case. Temporal waveforms were obtained for the pump and output pulses in order to evaluate the extent of tracking, and to study the mechanisms for loss of tracking. The highest laser efficiency observed was 43 percent for Oxazine 725 in MPMMA for a 2-mm thick sample. This material had a laser wavelength of approximately 690 nm for R_oc < 0.70. The value increased to approximately 735 nm, however, for R > 0.80. The longest output wavelength observed in this study was approximately 797 nm for Rhodamine 800 in PFNPG. The highest efficiency observed for this particular sample was 21 percent. Its emission wavelength was relatively insensitive to feedback over the range studied. Measurements of laser threshold are presented and discussed for the materials investigated.

The self-mixing effect of a microchip laser is applicable to optical CT (Computed Tomography) because of high sensitivity to weak light of the effect. Two acousto-optic modulators were used to frequency-shift the output beam from a microchip laser by several megahertz. The beam was attenuated by passing it through a scattering object and then re-injected into the microchip laser's cavity. The self-mixing effect modulated the output intensity of the laser at a frequency of several megahertz, and the intensity of modulation was measured by a spectrum analyzer. With a ring-type optical path, which is considered to be adequate for optical CT because the light only passes through the object once, it was possible to detect a beam attenuated by more than -90 dB by neutral density filters (ND filters), and to detect a beam attenuated by INTRALIPID-10 percent solution with a concentration of 28 percent, which has the same scattering-absorption characteristic as biological tissue. By Adjusting the frequency-shift towards the relaxation-oscillation frequency of the microchip laser increased the thickness of INTRALIPID-10 percent through which transmission was possible by a factor of two. Imaging through a scattering object by using this method was demonstrated.

The photophysical and lasing properties of a benzo-fused pyrromethene dye that is capable of being pumped by a diode or dye laser at relatively long wavelengths have been investigated for liquids and for a solid matrix, poly(methyl methacrylate) (PMMA). Fluorescence data, including quantum efficiency and lifetime, have been obtained. The dye emission, that is centered around 690 nm, shows good quantum efficiency as compared to other NIR dyes such as oxazine 1 or rhodamine 800. Photostability in organic solvents as well as the survivability of the dye under conditions of radical polymerization have also been investigated.