Srinivasa Ragam

Compact and portable terahertz source by mixing two frequencies generated simultaneously by a single solid-state laser

By mixing two frequencies generated from a single Q-switched Nd:YLF laser in a GaSe crystal, an average terahertz output power reaches 1 μW within a bandwidth of 65 GHz at 1.64 THz.

Power scalability and frequency agility of compact terahertz source based on frequency mixing from solid-state lasers

We investigate power scalability and frequency agility of a terahertz (THz) source by mixing two frequencies generated by solid-state lasers in a nonlinear crystal. They are made possible by introducing two solid-state laser crystals sharing the same Q switch and output coupler with the same laser beams decoupled to each other by a polarizer. Following the optimization, we have improved the THz output power nearly fivefold at 1.64 THz. By replacing one of the neodymium-doped lithium yttrium fluoride crystals with a neodymium-doped yttrium aluminum garnet crystal, we have produced 2.1 μW at 2.98 THz.

Singly resonant optical parametric oscillator based on adhesive-free-bonded periodically inverted KTiOPO 4 plates: terahertz generation by mixing a pair of idler waves

We implemented a singly resonant optical parametric oscillator based on adhesive-free-bonded periodically inverted KTiOPO4 plates. It has major advantages such as walk-off compensation and oscillation at four wavelengths. The threshold of the oscillation was measured to be 8 MW/cm2, which is about a factor of 4 lower than that based in two separate KTiOPO4 crystals. By frequency-mixing the dual-wavelength output in GaP stacks, we generated the terahertz radiation at 2.54 THz. The tuning range of the terahertz output was demonstrated to be 2.19-2.77 THz.

Investigation of terahertz generation from passively Q-switched dual-frequency laser pulses.

When two Nd:YLF crystals share a Cr:YAG crystal functioning as a single passive Q switch, the timing jitter between each pair of dual-frequency pulses generated by the two crystals has been reduced by a factor of 20. Such a reduction in the timing jitter allows us to generate terahertz pulses by focusing such a passively Q-switched laser beam onto a nonlinear crystal. Such a result represents the first step for us to eventually implement a compact terahertz source based on ultracompact microchip lasers.

Terahertz intracavity generation from output coupler consisting of stacked GaP plates

We demonstrate intracavity terahertz generation from an output coupler of a compact dual-frequency solid state laser. The output coupler consisting of unbonded and stacked GaP plates is used as a second-order nonlinear medium where the difference-frequency generation takes place. When quasi-phase matching is achieved within the alternatively rotated GaP plates, terahertz output power is significantly enhanced compared with that for the corresponding external-cavity configuration.

Compact and portable terahertz source by mixing two frequencies generated simultaneously by single solid-state laser

By mixing two frequencies generated from a single Q-switched Nd:YLF laser in a GaSe crystal, an average terahertz output power reaches 1 μW within a bandwidth of 65 GHz at 1.64 THz.

Singly-resonant optical parametric oscillator in adhesive-free-bonded periodically inverted KTiOPO 4 plates: Achieving oscillations at dual wavelengths

Based on adhesive-free-bonded periodically inverted KTiOPO4 plates, we implemented a singly-resonant optical parametric oscillator, which has superior advantages of compensating walk-off and oscillating dual-signal wavelengths based on QPM.

Generation of terahertz pulses by mixing dual-frequency pulses from Yb:YAG laser

We have demonstrated that terahertz pulses at 1.65 THz can be generated by mixing dual-frequency pulses emitted from a compact broadband Q-switched Yb:YAG laser.

Intracavity terahertz generation in laser output coupler made from stacked GaP plates

Efficient terahertz pulses are emitted from stacked GaP plates used as an output coupler for a Q-switched solid-state laser. Such a novel intracavity configuration is exploited to achieve an enhancement of two orders of magnitude.

Power scaling of actively Q-switched synchronized dual-frequency laser pulses based on two Nd:YLF crystals

By introducing two Nd:YLF crystals into two laser cavities as a new configuration, we have scaled up the total output power of actively Q-switched synchronized dual-frequency laser pulses by more than 6 times.