On-Demand Dynamic Terahertz Polarization Manipulation Based on Pneumatically Actuated Metamaterial.

In this paper, a new tuning strategy is proposed by incorporating a pneumatically actuated metamaterial to achieve on-demand polarization manipulation at THz frequencies. Through controlling the actuation pressure, the device function can be flexibly switched among three types of polarization conversion capabilities within the same operation frequency band, from 1.3 THz to 1.

Passive source depth estimation using beam intensity striations of a horizontal linear array in deep water.

Source depth estimation is an important yet very difficult task for passive sonars, especially for horizontal linear arrays (HLAs). This paper proposes an efficient two-step depth estimation scheme using narrowband and broadband constructive and deconstructive striation patterns due to interference between the direct (D) and sea surface reflected (SR) arrivals at an HLA on the bottom of deep water. First, the horizontal source-array ranges are derived from triangulation results of solid angle estimates by subarray beamforming.

Ultra-low noise phase measurement of fiber optic sensors via weak value amplification.

The noise floor is a vital specification that determines the minimum detectable signal in the phase measurement. However, the noise floor in optical phase measurement conducted via conventional optical interferometry tends to approach the intrinsic limit. In this study, a low noise phase measurement of a fiber optic sensor conducted via weak value amplification is experimentally demonstrated.

Visibility properties of the interferometric optical fiber sensors using polarization scrambling.

An interferometric optical fiber sensor relies on the coherent mixing of the optical signals, which is strongly polarization dependent. Random fluctuations in the input state of polarization and the polarization properties of the optical fiber sensor can result in the variation of the visibility and signal fading. Polarization scrambling is an important method to eliminate the input-polarization-induced fading.

Detecting mode hopping in single-longitudinal-mode fiber ring lasers based on an unbalanced fiber Michelson interferometer.

A method of detecting mode hopping for single-longitudinal-mode (SLM) fiber ring lasers has been proposed and experimentally demonstrated. The method that is based on an unbalanced Michelson interferometer (MI) utilizing phase generated carrier modulation instantly transforms mode-hopping dynamics into steep phase changes of the interferometer. Multiform mode hops in an SLM erbium-doped fiber ring laser with an 18.

Transient reflectance spectra of adaptive filters based on dynamic population gratings.

We propose a novel and practical method to exactly measure the transient reflectance spectra (TRS) of the adaptive filters based on dynamic population gratings. The modulating signals applied to the laser source play an important role. We specially designed a train of triangular amplitude modulated pulses with a small duty to modulate the laser frequency, and then the TRS was obtained from the grating responses to this pulse train.

Intensity noise and relaxation oscillation of a fiber-laser sensor array integrated in a single fiber.

We modeled the intensity noise of a distributed-feedback fiber laser (DFB-FL) with external laser injection. The transfer function for injected power perturbation was obtained. Simulation indicates that the laser relaxation oscillation frequency is not affected by external laser injection and is determined by the laser pump power, which provides a promising way to investigate the actual pump power budget over the whole wavelength-division multiplexing (WDM) fiber-laser sensor array integrated in a single fiber.

Relaxation oscillation in Er3+-doped and Yb3+/Er3+ co-doped fiber grating lasers.

Relaxation oscillations in Er(3+)-doped and Yb(3+)/Er(3+) co-doped fiber grating lasers were investigated. Intensity noise models were established for both cases in which the fluctuations of pump power and cavity loss were analyzed. Simulation indicates that the relaxation oscillation is induced by the pump power fluctuation, and fluctuation of the cavity loss can broaden the relaxation oscillation peak and enhance the amplitude.