Mahendra G. Jani

Room-temperature lasing of end-pumped Ho:Lu(3)Al(5)O(12).

Room-temperature lasing at 2.1-microm has been demonstrated in Ho:Lu(3)Al(5)O(12) with a slope efficiency of 82% and a threshold energy of 4.4 mJ. A maximum absorbed energy of 17 mJ yielded 10 mJ of laser output energy. To simulate diode-pumping experiments, a tunable Co:MgF(2) laser operating at 1.878 microm was used to achieve lasing on (5)I(7) ? (5)I(8) transitions.

DIODE-PUMPED, ROOM-TEMPERATURE TM:LUAG LASER

A diode-pumped, room-temperature Tm:LuAG laser demonstrated a total optical-to-optical efficiency of 0.073 and an optical-to-optical differential efficiency as high as 0.236. Laser performance and operating wavelength were investigated as a function of the Tm concentration. The highest laser output energy was achieved with a Tm concentration of 0.04 and at a wavelength of 2.0238 µm.

Spectral dynamics of laser-pumped Y3Al5O12:Tm,Ho lasers

Abstract The spectroscopic properties and energy transfer rates of Tm3+ and Ho3+ ions in Y3Al5O12:Tm,Ho (Tm,Ho:YAG) have been investigated. The dynamics of optical pumping in both the visible and near infra-red spectral regions were studied to establish rates for the various processes involved in laser-pumped Tm,Ho:YAG laser systems. Infrared to visible upconversion processes were investigated using dual wavelength excitation. The results of these experiments were used in a rate equation model to simulate laser operation.

Diode-pumped Ho:Tm:LuLiF/sub 4/ laser at room temperature

A diode-pumped room-temperature Ho:Tm:LuLiF/sub 4/ laser achieved an optical efficiency of 9.4% under normal mode operation. Under similar experimental conditions. Ho:Tm:LuLiF/sub 4/ yielded 1.5 times greater optical efficiency than Ho:Tm:YLiF/sub 4/. Absorption spectra and lifetimes as a function of pump energy were measured for evaluation of this laser material.

ZnGeP 2 parametric amplifier

A ZnGeP2 parametric amplifier was constructed, and the small-signal gain of a 3.39-μm He–Ne laser in excess of 10 was measured. With a 2.06-μm Ho:Tm:Er:YLF laser having a nominal 50-ns pulse length as a pump, small-signal gain was measured as a function of pump power. When compared with the predicted gain, taking into account the beam profile of both the pump and the signal, good agreement was found at low pump powers. However, the observed gain was less than predicted at higher pump powers. Pump-induced loss at 3.39 μm, a phenomenon not observed in other nonlinear crystals such as AgGeSe2, causes the difference. Pump-induced loss was observed when the ZnGeP2 crystal was tilted away from the phase-matching angle. Pump-induced loss at 3.39 μm was characterized and found to be directly proportional to the pump energy.

Electron spin resonance and optical studies of oxygen vacancy centers in quartz

A variety of paramagnetic oxygen-vacancy-associated defects are produced by ionizing radiation in alpha-quartz. These are the E-type centers. A survey of the current status of defect models for the E′1, E′4, and three E″ centers is presented. This includes descriptions of their electron-spin-resonance spectra and their production and thermal decay characteristics.

Alexandrite-laser excitation of a Tm:Ho:Y 3 Al 5 O 12 laser

Laser-pumped laser characteristics of a Tm:Ho:Y3Al5O12(YAG) crystal were measured as a function of the wavelength and energy of the alexandrite-laser pump source. Laser thresholds and slope efficiencies were recorded for 765-, 780-, and 785-nm pump wavelengths. Simultaneous laser emission was observed at 2.060, 2.065, 2.097, and 2.101 μm, and the relative intensities of these peaks were measured as a function of absorbed pump energy. Changes in temporal and spectral profiles of the laser emission were observed with variations in absorbed pump energy. When measurements were made with a monolithic crystal cavity instead of an open cavity, laser emission from Ho3+ was observed at 2.097 μm, and an additional laser peak was observed that may be due to transitions of the Tm3+ ions.

Lasing properties of chromium-aluminum-doped forsterite pumped with an alexandrite laser

The lasing properties of chromium-aluminum-doped forsterite were investigated using a tunable alexandrite laser as the pump source. Results of measurements of the lasing threshold, slope efficiency, spectral and temporal profiles of the laser pulse, and the time delay between the alexandrite pump pulse and the laser emission are presented for pump wavelengths of 770, 746, and 730 nm and different pump beam energies. Laser rate equations are developed to model the lasing center as a four-level system and applied to the case of 746-nm pumping. >

Long-pulse-length 2 μm diode-pumped YLiF 4 laser

A diode-pumped Ho:Tm:YLiF4 laser at room temperature has achieved an optical efficiency of 5.9% under normal-mode operation. Long pulse lengths, of the order of 1 μs, have been obtained by use of 4-m ring resonator, with laser energy output of 15 mJ in single Q-switched pulses for an input energy of 2.078 J.

Pump wavelength tuning of optical parametric oscillations and frequency mixing in KTiOAsO4

The properties of alexandrite laser‐pumped optical parametric oscillators are reported for potassium titanyl arsenate. Near infrared tuning curves and slope efficiencies were measured as functions of pump wavelength and pump power. In addition, sum frequency mixing of red and infrared wavelengths to produce green emission is also reported.