Yiquan Wang

Diffraction of digital micromirror device gratings and its effect on properties of tunable fiber lasers

A digital micromirror device (DMD) is a kind of widely used spatial light modulator. We apply DMD as wavelength selector in tunable fiber lasers. Based on the two-dimensional diffraction theory, the diffraction of DMD and its effect on properties of fiber laser parameters are analyzed in detail. The theoretical results show that the diffraction efficiency is strongly dependent upon the angle of incident light and the pixel spacing of DMD. Compared with the other models of DMDs, the 0.55 in. DMD grating is an approximate blazed state in our configuration, which makes most of the diffracted radiation concentrated into one order. It is therefore a better choice to improve the stability and reliability of tunable fiber laser systems.

Lasing characteristic of organic octagonal quasicrystal slabs with single-defect microcavity at low-index contrast.

We experimentally demonstrate and characterize an organic octagonal quasicrystal slab with a single-defect microcavity at low-index contrast. The gain medium is the conjugated-polymer, composed by two PPV derivatives, a BEHP-PPV and a MEH-PPV. By optical pumping, the lasing action is achieved at 607 nm with a FWHM of 1 nm. The threshold of lasing is 9 μJ/cm(2). The intensity of the lasing peak depends linearly on the pump energy above the threshold.

Tunable polarization-maintaining single-mode fiber laser based on a MEMS processor

A tunable from the C-band polarization-maintaining single-mode fiber laser is proposed based on a MEMS processor. The MEMS processor can select any part of the gain spectrum from the EDFA into a fiber ring, leading to a high-quality laser output.

Polarization Beam Splitter Based on the Self-Collimation of the Two-Dimensional Metallic Photonic Crystal

Self-collimation characteristics of the two dimensional metallic photonic crystals are studied for the TM and TE polarizations, respectively. The Drude dispersion model is adopted to describe the metal and the self-collimation behaviors for the TM and TE light beams along different directions are obtained for the near-infrared light waves. And a polarization beam splitter based on above structure is designed, which can avoid the output light propagating direction is influenced by the alteration of the incident direction of light beam within a certain region.

Electrically driven quasicrystal microcavity laser based on organic semiconductor

We design and fabricate an electrical pumping laser with a quasicrystal microcavity based on MEH-PPV layer sandwiched between two electrodes. The lasing performance is observed at 606 nm. The threshold current is around 0.8 mA.

Demonstration of 1×32 LCOS-based wavelength selective switch

In recent years, reconfigurable optical add drop multiplexers (ROADM) and multiple-dimensions optical cross-connection (OXC), as the essential devices of next-generation dynamic optical networks, have been attracted great interests by research institutions and relevant industry. 1×N Wavelength selective switches (WSSs) are one of the key components in current and next generation ROADM. Currently, WSS primarily rely on micro-electromechanical systems (MEMS) and liquid crystal on silicon spatial light modulators (LCOS-SLM) switches. LCOS-based WSSs have several advantages, including flexible spectrum coverage, adaptive alignment, and robustness. Based on a novel 2-f optical structure, we therefore propose 1×32 WSS system including a 1×32 fiber-coupling lenslet arrays, a collimating lens, a transmission grating, a cylindrical lens and a LCOS-SLM. By uploading the optimized phased holograms on the LCOS, we have successfully switched input signal with arbitrary wavelength in C-band into any output port. The output channel spacing can be adjusted flexibly and each port switches independently. Experimental results demonstrate the insertion loss is around 5~10dB and the switch crosstalk at 1550nm is -35dB. The 3dB-bandwidth of signal@100G is 40G.The research has established the theory and experiment foundation for the development of M×N WSS in future.

Organic octagonal quasicrystal mircocavity lasers based conjugated-polymer material with ultralow refractive-index

We experimentally demonstrate and characterize an organic octagonal quasicrystal slab with a single-defect microcavity at low-index contrast. The gain medium is the conjugated-polymer, composed by two PPV derivatives, a BEHP-PPV and a MEH-PPV. By optical pumping, the lasing action is achieved at 607 nm with a FWHM of 1nm. The threshold of lasing is 9uJ/cm2. The intensity of the lasing peak depends linearly on the pump energy above the threshold.

Engineering the Optical Transmission Enhancement through the Air Holes in a Metallic Film

Optical transmission enhancements of the metallic film with air holes are studied. The results show that the location of the resonant peak wavelengths are sensitive to the length of arrays periodicity, while the width of the extraordinary transmission wavelength region can be adjusted by altering the side length of square holes. The light intensity distributions through the air holes indicate that the near-field intensity is greatly enhanced. When the shape of the air holes is changed from a square to a rectangle, the transmission efficiency is quite sensitive to the direction of the incident electric fields polarization, which can be used as a simple optical polarization-choosing device.

Tailoring the Multi-Channel Filtering Properties of the Near-Infrared Photonic Crystal with Oval Air Holes

Optical characteristics of the multi-channel filters based on the two-dimensional photonic crystals with oval defects are studied. Shape alteration of the air hole from a circle to an ellipse offers a powerful approach to engineer the resonant wavelength of channel filters. It is found that the resonant wavelength can be flexibly adjusted only by changing the ovals obliquity. A six-channel side-coupled drop filters based on the oval holes with different obliquities is designed, and a good wavelength filtering ability is obtained.

High stable single-polarization tunable fiber laser based on Opto-DMD processor and polarization-maintaining fiber devices

A high stable wavelength-tunable fiber laser is experimentally demonstrated by using a digital-micromirror-device (DMD) processor and a polarization-maintaining erbium-doped fiber amplifier (EDFA).The electronic-addressed DMD processor is able to select and couple a waveband from of the polarization-maintaining EDFA back into the fiber ring to generate a narrow line-width laser output. The tunable fiber laser shows a line-width of 0.02nm, a tuning step of 0.08nm over the c-band and a side mode suppression ratio (SMSR) greater than 50 dB. The output power uniformity of 0.016dB is achieved by using the automatic power control (APC) system under room temperature. The center wavelength fluctuation during 1 hour is below 0.01 nm.