Generation of Fourier-transform-limited 35-ns pulses with a ramp-hold-fire seeding technique in a Ti:sapphire laser

A Hybrid Self-Seeded Ti:sapphire Laser with a Pumping Scheme Based on Spectral Beam Combination of Continuous Wave Diode and Pulsed DPSS Lasers

A wide variety of applications require high peak laser intensity in conjunction with a narrow spectral linewidth. Typically, injection-locked amplifiers have been employed for this purpose, where a continuous wave oscillator is amplified in a secondary external resonant amplifier cavity using a pulsed pump laser. In contrast, here we demonstrate a setup that combines a CW Ti:sapphire oscillator and pulsed amplifier in a single optical cavity, resulting in a compact system. Dichroic beam combination of blue wavelength semiconductor diodes and the green wavelength of a Nd:YAG laser allowed the simultaneous excitation of the Ti:sapphire crystal by both continuous wave and pulsed pump sources. A linewidth of <2MHz is achieved in continuous wave operation, while the linewidth increases to about 10MHz in the combined CW + pulsed mode with a pulse duration of 73ns. A peak pulse intensity of 0.2kW is achieved, which should enable efficient single-pass second harmonic generation in a nonlinear crystal.

Injection-seeded single-longitudinal-mode Ti:Sapphire laser with no active stabilization

We report on the first injection-seeded nanosecond Ti:Sapphire laser that demonstrates a stable single-longitudinal-mode operation with no feedback loop for active cavity stabilization. The short cavity generates 6-mJ transform-limited pulses at a wavelength of 807 nm and with a slope efficiency of 43%. An intracavity dispersive prism makes a novel cavity design for injection-seeded lasers and provides pre-selection of the emission wavelength. In support of these experiments, we perform numerical simulations that include extra cavity losses. The simulation results are in good agreement with the outcome of the experiment and reveal the formation scenario of the laser mode.

Injection seeded single-frequency pulsed Nd:YAG laser resonated by an intracavity phase modulator

A reliable single frequency Q-switched Nd:YAG laser is developed by using a lithium niobate crystal as the intracavity phase modulator. Successful injection seeding is performed by adopting an electro-optic crystal in an effectively simplified cavity arrangement. The laser is capable of producing 4.8 mJ pulse-energy at 400 Hz repetition rate with nearly Fourier-transform-limited spectral linewidth. The pulse duration is approximately 25 ns, and the beam quality factor M² is less than 1.3.

Stable and tunable single frequency Nd:GSAG laser around 943 nm

Stable single frequency output around 943 nm was obtained from a quasi-continuous wave (qcw) diode-pumped, Q-switched Nd:GSAG laser. The Q-switched Nd:GSAG laser was injection seeded with a single mode laser diode. Its frequency was stabilized by an active-control loop specially designed for a strong qcw pump. The spectral linewidth of the Nd:GASG laser was 41 MHz and the frequency stability was 10 MHz. The single-frequency-pulsed laser generated 32 mJ pulse energy at 10 Hz repetition rate. When the repetition rate was increased to 100 Hz, 5.6 mJ pulse energy was obtained by a thermal dynamic stable resonator. By tuning the seed laser, the wavelength of the pulsed Nd:GASG laser can be continuously varied from 942.1 to 943.1 nm.

High-power Ti:sapphire laser at 820 nm for scanning ground-based water-vapor differential absorption lidar

The Ti:sapphire (TISA) laser transmitter of the mobile, three-dimensional-scanning water-vapor differential absorption lidar (DIAL) of the University of Hohenheim is described in detail. The dynamically-stable, unidirectional ring resonator contains a single Brewster-cut TISA crystal, which is pumped from both sides with 250 Hz using a diode-pumped frequency-doubled Nd:YAG laser. The resonator is injection seeded and actively frequency-stabilized using a phase-sensitive technique. The TISA laser is operating near 820 nm, which is optimum for ground-based water-vapor DIAL measurements. An average output power of up to 6.75 W with a beam quality factor of M2<2 is reached. The pointing stability is <13 μrad (rms), the depolarization <1%. The overall optical-optical conversion efficiency is up to 19%. The pulse length is 40 ns with a pulse linewidth of <157 MHz. The short- and long-term frequency stabilities are 10 MHz (rms). A spectral purity of 99.9% was determined by pointing to a stratus cloud in low-elevation scanning mode with a cloud bottom height of ≈2.4 km.

Frequency stabilization of a single-frequency Q-switched Tm:YAG laser by using injection seeding technique

A stable single-frequency Q-switched Tm:YAG laser was demonstrated. The laser was injection seeded by a monolithic nonplanar ring oscillator laser utilizing the ramp-hold-fire technique. The measurements of the output parameters were presented. This paper focused on investigation of the frequency stability of the injection-seeded laser, which was measured by optical heterodyne technique. A method used to restrict the frequency jitter of the laser was discussed. The fluctuation of the laser frequency was reduced from 2.36 MHz (rms) to 1.07 MHz (rms) in 1 h by optimizing the voltage of the piezoelectric translator.

Nonlinear compression of Q-switched laser pulses to the realm of ultrashort durations

Mode-locked lasers have an undisputed position in the ultrafast domain, though they are fairly expensive for miscellaneous applications. Thus, laser consumers revert to more cost-effective systems like Q-switched lasers. Here we report on the nonlinear compression of passively Q-switched laser pulses that allows accessing the time domain of sub-10-picoseconds, which has been so far the realm of mode-locked lasers. Laser pulses with an initial duration of 100 ps from a passively Q-switched microchip laser are amplified in a photonic crystal fiber and spectrally broadened from 20 pm to 0.68 nm by self-phase modulation. These pulses are compressed in a grating compressor to a duration of 6 ps with a pulse energy of 13 µJ.

Single-frequency operation of diode-pumped 2 microm Q-switched Tm:YAG laser injection seeded by monolithic nonplanar ring laser

We present a diode-pumped, 2mum single-frequency Q-switched Tm:YAG laser. The Q-switched laser is injection seeded by a monolithic Tm:YAG nonplanar ring oscillator with the ramp-hold-fire technique. The output energy of the 2mum single-frequency Q-switched pulse is 2.23mJ, with a pulse width of 290ns and a repetition rate of 200Hz. From the heterodyne beating measurement, the frequency difference between the seed laser and the Q-switched laser is determined to be 37.66MHz, with a half-width of the symmetric spectrum of about 2 MHz.

Single frequency operation of a tunable injection-seeded Nd:GSAG Q-switched laser around 942nm

Single frequency operation of a diode-pumped tunable injection-seeded Nd:GSAG Q-switched laser around 942nm was demonstrated. With a three-mirror ring cavity, the single frequency laser pulse with output energy of 13.2mJ was obtained at a repetition rate of 10Hz. The linewidth of the single frequency laser was less than 100MHz. The wavelength of the single frequency Nd:GSAG laser can be tuned from 942.38nm to 943.10nm.

Chirp-corrected, nanosecond Ti:sapphire laser with 6 MHz linewidth for spectroscopy of antiprotonic helium

A nanosecond titanium sapphire laser with spectral linewidth Gamma(pl)~6 MHz and pulse energy of 50-100 mJ was demonstrated by using an intracavity electro-optic modulator to correct the frequency chirp in the output beam. The laser was referenced against a femtosecond frequency comb and used to measure the 6s-8s (F=4) two-photon transition frequency of Cs with a precision of 1.4 parts in 10(9).

Development of a 1.6 microm differential absorption lidar with a quasi-phase-matching optical parametric oscillator and photon-counting detector for the vertical CO2 profile

We have developed a 1.6 microm carbon dioxide (CO(2)) differential absorption lidar utilizing a quasi-phase-matching optical parametric oscillator (OPO) and a photon-counting detector. The operating wavelengths were chosen based on their low interference from water vapor and low temperature sensitivity. The online wavelength was in the (30012<--0001) band of CO(2), which was insensitive to atmospheric temperature. The established OPO laser achieved a 10 mJ, 200 Hz repetition rate at the online and offline wavelengths. Our observations confirmed the statistical error of 2% with 5 h of accumulation for the CO(2) density profile less than 5.2 km. Also, the statistical error of 1% at an altitude of 2 km was demonstrated. The results of the vertical CO(2) concentrations acquired using a 1.6 microm wavelength are presented.

Airborne high spectral resolution lidar for profiling aerosol optical properties

A compact, highly robust airborne High Spectral Resolution Lidar (HSRL) that provides measurements of aerosol backscatter and extinction coefficients and aerosol depolarization at two wavelengths has been developed, tested, and deployed on nine field experiments (over 650 flight hours). A unique and advantageous design element of the HSRL system is the ability to radiometrically calibrate the instrument internally, eliminating any reliance on vicarious calibration from atmospheric targets for which aerosol loading must be estimated. This paper discusses the design of the airborne HSRL, the internal calibration and accuracy of the instrument, data products produced, and observations and calibration data from the first two field missions: the Joint Intercontinental Chemical Transport Experiment--Phase B (INTEX-B)/Megacity Aerosol Experiment--Mexico City (MAX-Mex)/Megacities Impacts on Regional and Global Environment (MILAGRO) field mission (hereafter MILAGRO) and the Gulf of Mexico Atmospheric Composition and Climate Study/Texas Air Quality Study II (hereafter GoMACCS/TexAQS II).

Quasi-Fourier-transform limited, scannable, high energy titanium-sapphire laser source for high resolution spectroscopy

A tunable injection seeded Ti:sapphire laser source has been developed and tested. Slave-master tandem cavity and ramp-lock-and-fire concepts have been implemented and fully controlled by a digital signal processor. A Fourier-transform-based analysis, as well as direct measurements, have demonstrated spectral linewidths in the range of 3.5-15 MHz (HWHM), with potential tunability over the entire Ti:sapphire lasing range. A quasi-Fourier-transform limited spectral linewidth is demonstrated assuming a secant hyperbolic shape of the electromagnetic field. Output energies >100 mJ have been reached with approximately 300 mJ of pump energy. The highest spectral purity is obtained using the quadruple pumping scheme.

Injection-seeded pulsed Ti:sapphire laser with novel stabilization scheme and capability of dual-wavelength operation

A gain-switched, single-frequency titanium-sapphire laser for atmospheric humidity measurements using the differential absorption lidar technique operating in the 820 nm wavelength region is described. The laser is pumped by a frequency-doubled, flashlamp-pumped Nd:YAG laser at a repetition rate of 50 Hz and injection seeded by two external-cavity-diode lasers. The system yields pulses with an energy of 15 mJ and high spectral purity. We describe a novel active injection-locking technique that avoids the problems of established methods like dither-lock or ramp-and-fire. Furthermore, our method opens the possibility to switch between two wavelengths for alternating shots, in contrast to most established techniques that only allow operation at one wavelength.