Publications by authors named "H Ishizuki"

Millijoule-scale pulses of multicycle terahertz radiation (MC-THz) are increasingly being pursued as drivers for applications requiring high-fields and high spectral brightness. An attractive approach for generating high peak-power MC-THz pulses is nonlinear optical down-conversion of laser pulses in periodically-poled crystals. A principal limitation to the yield, however, is the small (sub-centimeter) apertures of commercially-available crystals which restrict the amount of laser energy that can be used.

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Article Synopsis
  • The study discusses the development of a singly resonant optical parametric oscillator leveraging a 5% MgO:PPLN partial cylinder and a sub-nanosecond microchip laser that operates at 1064 nm frequency with a 1 kHz repetition rate.
  • The oscillator is capable of continuous wavelength tuning ranging from 1410 nm to 4330 nm through the rotation of the cylinder.
  • The system produces several microjoules of energy and maintains a beam quality factor M of less than 3, indicating effective beam performance.
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Stress-induced polarity inversion of crystal quartz using a quasi-phase matching (QPM) stamp is proposed for a QPM frequency conversion quartz device. Fabrication of QPM structure in x-cut quartz plate could be realized using the periodically patterned QPM stamp. Also, second-harmonic 532 nm generation with 16.

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Highly-efficient optical generation of narrowband terahertz radiation enables unexplored technologies and sciences from compact electron acceleration to charge manipulation in solids. State-of-the-art conversion efficiencies are currently achieved using difference-frequency generation driven by temporal beating of chirped pulses but remain, however, far lower than desired or predicted. Here we show that high-order spectral phase fundamentally limits the efficiency of narrowband difference-frequency generation using chirped-pulse beating and resolve this limitation by introducing a novel technique based on tuning the relative spectral phase of the pulses.

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Crystal quartz has excellent optical properties as short absorption edge and high laser-damage threshold, which are suitable for intense pulse-laser pumped wavelength conversion by artificial quasi-phase matching structures. We present on initial evaluation of second-harmonic green generation with 14.9 kW peak power using periodic laminar structured quartz, pumped by sub-nanosecond pulse with focused intensity > 100 GW/cm.

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