Shoji Niki

Environmentally stable, simple passively mode-locked fiber ring laser using a four-port circulator

We present here a self-starting passively mode-locked fiber ring laser with a novel cavity configuration using a four-port optical circulator. Our special ring cavity design enables highly stable mode-locked operation between 25 and 60 degrees C to be maintained without the need for any polarization-adjusting devices. The pulse width and the integrated timing jitter from 10 Hz to 10 MHz of our fiber ring laser were measured to be 120 fs and 39.1 fs, respectively. As a result, a robust and environmentally stable all-fiber mode-locked fiber ring laser with a simple ring cavity configuration in a small package has been achieved.

Optical frequency standard by using a 1560 nm diode laser locked to saturated absorption lines of rubidium vapor

A robust, compact, highly accurate rubidium optical frequency standard module was developed to overcome the delicate performance of conventional frequency stabilized lasers. A frequency doubled 1560 nm distributed feedback diode laser locked to a rubidium D(2) saturated absorption line without using an optical amplifier was demonstrated, and dithering-free optical output was obtained. In addition, the sensitivity of the developed optical frequency standard to magnetic fields was investigated. We confirmed that the influence of the magnetic fields on the optical frequency standard can be almost negligible when using appropriate magnetic-shield films. As a result, the magnetic-field-insensitive optical frequency standard, which can be embedded in optical systems, exhibiting uncertainty less than at least 100 kHz, was successfully realized for the first time to the best of our knowledge.

Highly accurate Michelson type wavelength meter that uses a rubidium stabilized 1560 nm diode laser as a wavelength reference.

We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength. We describe a novel dual-wavelength self-calibration scheme that maintains high accuracy of the wavelength meter. The method uses the fundamental and second-harmonic wavelengths of an Rb-stabilized DFB diode laser. Consequently, a highly accurate Michelson type wavelength meter with an absolute accuracy of 5 x 10(-8) (10 MHz, 0.08 pm) over a wide wavelength range including optical communication bands was achieved without the need for a vacuum chamber.

Practical absolute wavelength meter using iodine-stabilized diode laser

A practical absolute wavelength meter was assembled separately a reference wavelength source and wavelength measurement system. The frequency (wavelength) stability was obtained to be 2×10-12 for a reference wavelength source. The other hand accuracy of wavelength measurement was estimated to be ** Michelson interferometer with vacuum chamber. The wavelength was estimated to be 1523.48813 nm for a 1523nm He-Ne laser as test laser. Moreover, the pressure dependence for wavelength was measured to be 0.0044 [pm/hPa]. Measurement reproducibility of the wavelength meter was guaranteed to be ±0.035pm.