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We demonstrate a master oscillator power amplifier (MOPA) system that emits single-frequency high-energy optical pulses at 1540 nm using an Er,Yb:glass planar waveguide amplifier and a large mode area Er-doped fiber amplifier. A double under-cladding and a 50-µm-thick core structure are employed for the planar waveguide amplifier to increase the output energy without degrading the beam quality. A pulse energy of 45.2 mJ with a peak power of 27 kW is generated at a pulse repetition rate of 150 Hz with a pulse duration of 1.7 µs. Moreover, the beam quality factor M2 of the output beam is 1.84 at the highest pulse energy thanks to its waveguide structure.

Waveguide-based devices are essential for highly efficient nonlinear optical conversion. However, the nonlinearity associated with the conversion in such devices is not self-evident. The authors present a method using optical frequency metrology to reveal the nonlinearity inside a waveguide, and establish that the spectral broadening in a periodically poled lithium niobate waveguide is due to quadratic nonlinearity. They also demonstrate absolute frequency measurement using the generated ultrabroadband comb. This study will contribute to the design of chip-scale, fully integrated devices for efficient nonlinear optical conversion.

We generate a broadband frequency comb using a WG-PPLN and measure the offset frequency of the comb by using a frequency-stabilized laser at 532 nm. The visible comb is generated through χ(2) process.

We have developed iodine-stabilized lasers using ultra-compact diode laser modules at 531, 561 and 594 nm. The achieved frequency stabilities were typically 4×10−13 at an averaging time of 1000 s.

We demonstrate high-resolution spectroscopy of molecular iodine using coin-sized laser modules at 531 nm, 561 nm, and 594 nm. Hyperfine components of the R(36)32-0, P(64)20-0, and P(69)12-1 transitions are observed with a signal-to-noise ratio of several tens over a bandwidth of 100 Hz. The laser modules are frequency-stabilized to the observed hyperfine components and achieve stabilities at a level of 10−12 for a 1-s averaging time. The frequency-stabilized coin-sized laser modules are useful for various applications, including interferometric measurements and studies of molecular iodine.