Santanu Basu

Continuous-wave mode-locked Nd:glass laser pumped by a laser diode.

We have demonstrated a diode-laser-pumped, cw, mode-locked Nd:glass laser oscillator. With a 0.5% output coupler the pump threshold for mode-locked operation was 22.9 mW. The mode-locked pulse width was shorter than 36.5 psec, which was the response time of the fast photodiode and the sampling oscilloscope. Diode-laser-pumped mode-locked operation was also extended to Nd:YAG.

Amplification in Ni-like Nb at 204.2 Å pumped by a table-top laser

We identified for the first time the 3d94d1S − 3d94p1P line in Ni-like Nb at 204.2 Å that was predicted to show gain. When pumped with a train of pulses containing less than 1 J per pulse, significant emission was recorded at 204.2 Å following the second and the third pulses. We measured the small signal gain coefficient per Joule of incident laser energy to be 1.49±0.42 cm−1 J−1 for this laser transition, which is higher by several orders of magnitude than that reported for other collisional laser systems in this wavelength range.

Average power limits of diode-laser-pumped solid state lasers

We investigated the average power limits of diode laser pumped slab lasers and present design calculations for several laser configurations. In the laser designs, a number of diode lasers, each one of which is coupled to an optical fiber are employed to pump a solid state laser material in a zigzag slab or a disk geometry. The systems described here can produce multiple kilowatts of average output power with currently available diode lasers in a cost-effective manner.

40-W average power, 30-Hz moving-slab Nd:glass laser

A moving-slab-geometry Nd:glass laser has been designed and demonstrated. An average power output of 43.8 W has been achieved at 2.76-kW input power and at 2.06% slope efficiency. The moving-slab laser has the potential for scaling to kilowatt average power levels.

Short pulse injection seeding of Q-switched Nd:glass laser oscillators-theory and experiment

A 0.5-GW-peak-power solid-state laser source that is based on injection seeding a Q-switched Nd:Glass laser is discussed. In the first experimental demonstration, a Q-switched oscillator producing 101 mJ was seeded by a train of 11-ps pulses from a CW (continuous-wave) mode-locked laser to produce injection-mode-locked pulses under a 91-ns envelope. A theoretical analysis of injection seeding of a high-gain Q-switched oscillator by the output of a mode-locked oscillator is presented. The numerical analysis predicts the minimum signal power required for injection mode locking and the temporal shape of the output pulse. The experimental results agree well with the theoretical predictions. The amplification demonstrated by this technique is 104.4 dB, which is much greater than that demonstrated by a multipass or regenerative amplifier. The experimental advantages of injection mode locking include greater than 100 dB of effective amplification and noncritical cavity length adjustment of the seed resonator. >

Design analysis of a short wavelength laser in an unstable resonator cavity

The use of diffractive output coupling and potentially easy fabrication make unstable resonators suitable for extreme ultraviolet and soft x‐ray lasers. We illustrate the design of an unstable resonator cavity for a proposed electron collisionally excited Ni‐like Mo laser at 191 A. Saturated output in a near‐diffraction limited beam is predicted in a six‐pass synchronously pumped cavity with a gain‐length product of 6.

A proposed 1 kW average power moving slab Nd:Glass laser

The design considerations of a high average power Nd : glass slab laser in which the slab moves between the pumping lamps to distribute the thermal loading over the area of the glass while maintaining high gain in the pumped volume are presented. Continuous wave operation and high repetition rate pulsed operation are projected at the 1kW average power level.

Diode-pumped moving-disc laser: a new configuration for high average power generation

In this paper we report a new geometry for diode laser pumping. We show that an efficient moving-disc laser can be designed which can operate at 20 kW of average power with existing diode laser technology.

Fractional power in the bucket, beam quality and M2

This paper gives expressions to calculate the fraction of power, fPIB, from a given multimode gaussian laser beam that can be deposited within a bucket of radius, rT, on a target at a range, zT, using a focusing optic of diameter, Df. We relate the power in the bucket, fPIB, to the M2 parameter, both of which can be experimentally measured. In this paper, we have also presented relationships between these two parameters and BQ and Strehl, which have not been unambiguously defined for a multimode laser beam in the literature. We propose fPIB and M2 to be used as standard design parameters instead of BQ and Strehl for laser-target interaction tests with multimode laser beams from stable resonators.

High-power Q-switched rotary disk lasers

Rotary disk laser has a very efficient thermal management approach that uses physical motion of the gain medium in a diode-pumped solid state laser. The benefits of rotary disk lasers over conventional bulk solid state lasers are high efficiency, power scalability and high peak power pulsed operation in a single-mode output beam. We have generated 72.8 W of TEM00 Qswitched output power at 50% slope efficiency in a crystalline Yb-YAG rotary disk laser.