Optical transmission of a moving Fabry-Perot interferometer.

Fabry-Perot interferometers have been widely studied and used for well over a century. However, they have always been treated as stationary devices in the past. In this Letter, we investigate the optical transmission of a longitudinally moving Fabry-Perot interferometer within the framework of relativity and establish a general relation between the transmission coefficient and the velocity for uniform motions.

A Glass-Fiber-Optic Turbidity Sensor for Real-Time In Situ Water Quality Monitoring.

Turbidity is an important water quality parameter, especially for drinking water. The ability to actively monitor the turbidity level of drinking water distribution systems is of critical importance to the safety and wellbeing of the public. Traditional turbidity monitoring methods involve the manual collection of water samples at set locations and times followed by laboratory analysis, which are labor intensive and time consuming.

Impact of Soil-Based Insulation on Ultrahigh-Resolution Fiber-Optic Interferometry.

High resolution optical interferometry often requires thermal and acoustic insultation to reduce and remove environment-induced fluctuations. Broader applications of interferometric optical sensors in the future call for low-cost materials with both low thermal diffusivity and good soundproofing capability. In this paper, we explore the feasibility and effectiveness of natural soil as an insulation material for ultrahigh-resolution fiber-optic interferometry.

Dynamic photoelectron transport in stepwise-doped GaAs photocathodes.

We present a theoretical model describing photoelectron transport dynamics in stepwise-doped GaAs photocathodes. Built-in electric field caused by the doping structure is analyzed, and the time-evolution of electron concentration in the active layer induced by a femtosecond laser pulse is solved. The predictions of the model show excellent agreement with the experimental data measured with pump-probe transient reflectometry, demonstrating the capability of the theoretical model in predicting photoelectron behaviors in real devices.

A Mach-Zehnder Fabry-Perot hybrid fiber-optic interferometer operating at the thermal noise limit.

A new type of interferometric fiber sensor based on a Mach-Zehnder Fabry-Perot hybrid scheme has been experimentally demonstrated. The interferometer combines the benefits of both a double-path configuration and an optical resonator, leading to record-high strain and phase resolutions limited only by the intrinsic thermal noise in optical fibers across a broad frequency range. Using only off-the-shelf components, the sensor is able to achieve noise-limited strain resolutions of 40 f[Formula: see text]/[Formula: see text] at 10 Hz and 1 f[Formula: see text]/[Formula: see text] at 100 kHz.

Impact of residual gas on the optoelectronic properties of Cs-sensitized InGaAs (001) surface.

Near-infrared InGaAs photocathode with better optoelectronic properties is a good candidate for low-light-level (LLL) night-vision system. However, the residual gases in the ultra-high vacuum (UHV) system inevitably affects the stability and photo-emission performance of LLL photoelectric devices such as their quantum efficiency and life-time. In this study, the first-principles calculations were used to investigate the adsorption effect of five different residual gas species, including H, CH, CO, HO and CO on Cs-sensitized InGaAs (001) β (2 × 4) surface.

Bidirectional, Bimodal Ultrasonic Lamb Wave Sensing in a Composite Plate Using a Polarization-Maintaining Fiber Bragg Grating.

Lamb wave (LW) is well suited for structural health monitoring (SHM) in advanced composites. However, characteristic differences between the symmetric modes and the anti-symmetric modes often add complexity to SHM systems. The anisotropic nature of composite materials, on the other hand, necessitates direction-sensitive sensing.

Dynamic optical sampling by cavity tuning and its application in lidar.

Optical sampling by cavity tuning (OSCAT) enables cost-effective realization of fast tunable optical delay using a single femtosecond laser. We report here a dynamic model of OSCAT, taking into account the continuous modulation of laser repetition rates. This allows us to evaluate the delay scan depth under high interferometer imbalance and high scan rates, which cannot be described by the previous static model.

Atmospheric transfer of a radio-frequency clock signal with a diode laser.

Remote transfer of a radio-frequency clock signal over a 60 m open atmospheric link has been experimentally investigated using a diode laser as the clock carrier. Phase-noise spectra and Allan deviations are both measured to characterize the excess clock instability incurred during the transfer process. Different detection schemes are used to assess the contributions from different noise sources.

Radio-frequency clock delivery via free-space frequency comb transmission.

We characterize the instability of an rf clock signal caused by free-space transmission of a frequency comb (FC) under typical laboratory conditions. The phase-noise spectra show the involvement of multiple random processes. For a 10 m transmission, the rms timing jitter integrated over 1-10(5) Hz is 95 fs, and the root Allan variance over 1 s is 4x10(-13).

Locking lasers with large FM noise to high-Q cavities.

We demonstrate that a laser can be directly locked to a cavity when the laser linewidth is much greater than the cavity linewidth. We lock an external-cavity diode laser with more than 1 MHz of added frequency noise to a 3.5 kHz wide cavity resonance.