Pin Han

Spectral anomalies for a right triangle aperture with an adjustable hypotenuse slope

The far-field spectral anomalies for a right triangle with an adjustable hypotenuse slope are studied. Through the derived analytic expression and numerical examples, the relation between phase singularities and spectral switches is clarified and the necessary condition for the existence of spectral switches is suggested. It is also shown that spectral switches can be controlled by simply adjusting the slope of the hypotenuse. This control mechanism has the benefit of easier implementation than other previous schemes which modulate some properties of the light source to achieve it. The way of using this method to perform the information encoding and transmission is also presented.

Adiabatic fiber microtaper with incorporated an air-gap microcavity fiber Fabry-Pérot interferometer

This study demonstrates an adiabatic fiber microtaper with incorporated an air-gap microcavity fiber-Fabry-Perot-interferometer to perform superior sensing characteristics. Optical interference fringes with good fringes contrast within bandwidth of 1250–1650u2009nm are performed experimentally. A highly spectral sensitivity of peak power with +3.65u2009dB/u2009°C (+9759u2009dB/RIU) is achieved when the device is operated under a fundamental-mode-cutoff (FMC) condition. By measuring peak power of the fringe, one can determine the temperature (T) or refractive index of environment. The proposed hybrid sensor is further applied to measure high T (∼1000u2009°C) of surrounding in non-FMC condition that obtains a good linearity of spectral response.

Electro-optic modulation for spectral switches and phase singularities of a double slit in the far field

It is shown that spectral switches of a double slit can be controlled by an electro-optic effect that has the benefit of high speed modulation without using any movable part of the aperture and this is a remarkable improvement compared with the schemes which use aperture mechanisms or a light source mechanism to perform this task. In particular, we find that phase singularities and spectral switches can be produced right at the center of the detection plane, which usually cannot be achieved by other mechanisms, and it should be a favorable property for data transmission usage. Also a data transmission scheme that utilizes the novel electro-optic phase modulation is presented.

Talbot images and Talbot spectra of a 2D orthogonal periodicity structure

The conditions for Talbot images and Talbot spectra associated with a 2D orthogonal periodicity structure are obtained with the transfer function method. It is found that the longitudinal distances to find the whole 2D Talbot images are the least common multiple of each of the individual 1D Talbot periodicities. Also, the transversal locations to find the Talbot spectra are given, where the detected spectra are identical to the incident one without the effect of diffraction. The spectral switches involved are also presented.

A data transmission scheme with spectral switches of a shifting double slit in the far field

A novel data transmission scheme that can be used for any desired transmitting direction in free space is introduced. This scheme is obtained by analyzing the analytic form of the diffracted spectrum of a coherent broadband Gaussian spectrum incident on a shifting double slit. The merits of this method are that the transmission angle can be chosen arbitrarily in advance and that it is easy to implement compared with other previous schemes which modulate some properties of the light source.

Spectral switches of a double slit with a movable central part in the far-field

The far-field spectral properties for a broad-band Gaussian spectrum incident on a double slit with a movable central part are investigated. The analytic expression is first derived and some numerical examples based on it are given to illustrate the anomalous behavior of the diffracted spectrum. It is found that the important effect called spectral switches can be controlled by simply moving the central part of the double slit. This control mechanism has the merit of easier implementation than previous schemes which modulate some properties of the light source (e.g. spatial coherence or spectral bandwidth) to achieve it.

Ultrasensitive microtaper with an air-gap microcavity fiber Fabry-Pérot interferometer

This paper demonstrates a microfiber incorporated with an air-gap microcavity fiber Fabry-Pérot-interferometer to achieve an ultrasensitive sensing characteristic. An extremely high sensitivity is achieved when the hybrid configuration operated under a fundamental-mode cutoff (FMC) condition.

A spectral flat-top, single resonant and ultrabroad band long-period fiber grating

A spectral flat-top, single resonant and ultra broadband—more than 180 nm in a −20dB bandwidth, thin-clad long-period fiber grating (LPG) with synthesizing using the Lagrange multiplier optimization (LMO) algorithm is presented in this paper.