Comb coherence-transfer and cavity ring-down saturation spectroscopy around 1.65μm: kHz-accurate frequencies of transitions in the 2ν3 band of 12CH4

Comb Coherence Transfer (CCT) uses a feed-forward frequency correction to transfer the optical phase of a frequency comb to the beam of a free-running diode laser. This allows to amplify...

Numerical analysis of optical phase modulator operating at 2 μm wavelength using graphene/III-V hybrid metal-oxide-semiconductor capacitor

We propose an optical phase modulator with a hybrid metal-oxide-semiconductor (MOS) capacitor, consisting of single-layer graphene and III-V semiconductor waveguide. The proposed modulator is numerically analyzed in conjunction with the surface conductivity model of graphene. Since the absorption of graphene at a 2 µm wavelength can be suppressed by modulating the chemical potential of graphene with the practical gate bias, the phase modulation efficiency is predicted to be 0.051 V·cm with a total insertion loss of 0.85 dB when an n-InGaAs waveguide is used, showing the feasibility of the low-loss, high-efficiency graphene/III-V hybrid MOS optical phase modulator, which is useful in the future 2-µm optical fiber communication band.

Terrestrial Planet Optical Phase Curves. I. Direct Measurements of the Earth

NASA’s EPOXI mission used the Deep Impact spacecraft to observe the disk-integrated Earth as an analog to terrestial exoplanets’ appearance. The mission took five 24 hr observations in 2008–2009 at various phase angles (57.°7–86.°4) and ranges (0.11–0.34 au), of which three equatorial (E1, E4, E5) and two polar (P1, North and P2, South). The visible data taken by the HRIV instrument ranges from 0.3 to 1.0 μm, taken trough seven spectral filters that have spectral widths of about 100 nm, and which are centered about 100 nm apart, from 350 to 950 nm. The disk-integrated, 24 hr averaged signal is used in a phase angle analysis. A Lambertian-reflecting, spherical planet model is used to estimate geometric albedo for every observation and wavelength. The geometric albedos range from 0.143 (E1, 950 nm) to 0.353 (P2, 350 nm) and show wavelength dependence. The equatorial observations have similar values, while the polar observations have higher values due to the ice in view. Therefore, equatorial observations can be predicted for other phase angles, but (Earth-like) polar views (with ice) would be underestimated.