Naoya Kuse

All polarization-maintaining Er fiber-based optical frequency combs with nonlinear amplifying loop mirror

A fully stabilized all polarization-maintaining Er frequency comb with a nonlinear amplifying loop mirror with below 0.2 rad carrier-envelope-offset frequency phase noise is demonstrated. The integrated timing jitter is measured as 40 attosecond from 10 kHz to 10 MHz, which is the lowest value of any Er fiber frequency comb to date.

Static FBG strain sensor with high resolution and large dynamic range by dual-comb spectroscopy.

We demonstrate a fiber Bragg grating (FBG) strain sensor with optical frequency combs. To precisely characterize the optical response of the FBG when strain is applied, dual-comb spectroscopy is used. Highly sensitive dual-comb spectroscopy of the FBG enabled strain measurements with a resolution of 34 nε. The optical spectral bandwidth of the measurement exceeds 1 THz. Compared with conventional FBG strain sensor using a continuous-wave laser that requires rather slow frequency scanning with a limited range, the dynamic range and multiplexing capability are significantly improved by using broadband dual-comb spectroscopy.

Ultra-low noise all polarization-maintaining Er fiber-based optical frequency combs facilitated with a graphene modulator.

High bandwidth carrier phase and repetition rate control are critical for the construction of low phase noise optical frequency combs. Here we demonstrate the use of a graphene modulator for the former and a bulk electro-optic modulator for the latter enabling record low phase noise operation of an Er fiber frequency comb. For applications that do not require carrier phase control, we show that the form factor of a fiber comb can be reduced by adapting a graphene modulator for rapid repetition rate control. Moreover, the whole system demonstration is performed with all-polarization maintaining Er fiber frequency combs, highly suitable for applications in the field.

Self-compensation of third-order dispersion for ultrashort pulse generation demonstrated in an Yb fiber oscillator.

Compensation of the intracavity dispersion in the mode-locked oscillator is known to be one of the most important factors for ultrashort pulse generation. However, recent investigations of a Yb-doped fiber mode-locked oscillator revealed that precise third-order dispersion (TOD) compensation is not always necessary for ultrashort pulse generation, owing to the strong nonlinearity that compensates residual TOD without reducing its spectral bandwidth. The origin of the nonlinear TOD compensation has remained unclear. To investigate the process in detail, we studied the pulse evolution inside a 30 fs Yb-doped fiber mode-locked oscillator both experimentally and numerically, and we found that the nonlinear phase shift with a temporally asymmetric pulse shape introduces an appropriate amount of TOD that exactly cancels the residual cavity dispersion.

Comb-Resolved Dual-Comb Spectroscopy Stabilized by Free-Running Continuous-Wave Lasers

We demonstrate dual-comb spectroscopy with relatively phase-locked two frequency combs, instead of frequency combs firmly fixed to the absolute frequency references. By stabilizing two beat frequencies between two mode-locked lasers at different wavelengths observed via free-running continuous-wave (CW) lasers, two combs are tightly phase locked to each other. The frequency noise of the CW lasers barely affects the performance of dual-comb spectroscopy because of the extremely fast common-mode noise rejection. Transform-limited comb-resolved dual-comb spectroscopy with a 6 Hz radio frequency linewidth is demonstrated by the use of Yb-fiber oscillators.

All-polarization-maintaining, single-port Er:fiber comb for high-stability comparison of optical lattice clocks

All-polarization-maintaining, single-port Er:fiber combs offer long-term robust operation as well as high stability. We have built two such combs and evaluated the transfer noise for linking optical clocks. A uniformly broadened spectrum over 135-285 THz with a high signal-to-noise ratio enables the optical frequency measurement of the subharmonics of strontium, ytterbium, and mercury optical lattice clocks with the fractional frequency-noise power spectral density of

Injection locking of Yb-fiber based optical frequency comb

(1-2)\times 10^{-17}

Low noise electro-optic comb generation by fully stabilizing to a mode-locked fiber comb.

Hz

Low noise, self-referenced all polarization maintaining Ytterbium fiber laser frequency comb

^{-1/2}

Fast ultra-wideband microwave spectral scanning utilizing photonic wavelength- and time-division multiplexing

at 1 Hz. By applying a synchronous clock comparison, the comb enables clock ratio measurements with