We fabricate low threshold current monolithic distributed feedback (DFB) laser with a multi-mode interface (MMI) combiner using butt-joint metal-organic chemical vapor deposition technology with different waveguide structures. Multi-layer mask self-aligned photolithography technology is used to form different waveguides in active and passive regions, respectively. The result shows that the laser threshold current is lower than 10 mA, with 50 dB side-mode suppression ratio.

We design and fabricate compact, low loss, and high port-count optical power splitters of 1 × 128 and2 × 128 using silica-based planar lightwave circuit (PLC) technology on 6 inch quartz substrate. PLC tech-nology is mainly based on plasma enhanced chemical vapor deposition, photolithography, and etching. The measured results show that the insertion loss, uniformity, and wavelength-dependent loss of 1 × 128 and 2 × 128 optical power splitters are less than 23, 1.43, and 0.92 dB and 23.3, 1.8, and 1.3 dB, respectively, in the wavelength range from 1.26 to 1.65 mm. The polarization-dependent losses are less than 0.16 and 0.2 dB, respectively, in the wavelengths of 1.31, 1.49, and 1.55 mm.

We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics as optical coupler. The model is based on numerical evaluation of electromagnetic wave by applying an intrinsic field integral to evaluate the field behaviour inside the optical waveguide. To analyse the field distribution inside the non-uniform waveguide and predict the beam propagation of optical energy involved in the propagation process, it is necessary to track the motion of any observation point along the tapered waveguide itself. Physically, the rays of the spectrum undergo reflections on the waveguide boundaries until the cut-off occurs and the phenomena of radiation begin. The numerical results show good agreement with those obtained by classical methods of evaluation used by other works.

A numerical simulation is performed to study the far-field diffraction properties of planar diamond waveguides. The far-field intensity distributions of a planar air waveguide and a diamond waveguide with different distances are given by numerical calculations. In the experiment, the diffraction patterns on the screen with different distances are recorded using a He-Ne laser as the light source, wherein the laser beam is coupled with and propagates in the diamond waveguide. The simulation results are found to be consistent with the experimental ones.

A compact bi-directional (BiDi) triplexer using grating-assisted multimode interference (MMI) coupler is proposed based on silicon nanowire waveguides.Because of the high index contrast between silicon and silicon dioxide, the size of the structure is greatly reduced with a footprint of 2.5 \times 911 (\mu m). Asymmetrical ports are introduced in the MMI structure to satisfy the bandwidth requirements of the industrial standards ITU-T G.983.3-dB bandwidths of 100, 22, and 15 nm are obtained for the wavelengths of 1 310, 1 490, and 1 550 nm, respectively. The device can be readily fabricated using a commercial CMOS process.

Modal filtering in nulling interferometer is based on the capability of single-mode waveguides to transmit only one complex amplitude function to eliminate virtually any perturbation of the interfering wavefronts. In this letter, we focus on realizing single-mode waveguide of chalcogenide glasses in the thermal infrared range 6–20 \mu m by burying a GASIR (Ge-As-Se) fiber core in the substrates of As-Se-S glasses system. To match the single-mode operation, GASIR fiber core of about 15-μm diameter is drawn, the fiber core is buried into As-Se-S substrates by heating two kinds of glasses to a suitable temperature. The propagation mode is tested by guiding a CO2 laser emitting at 9.3 μm into the waveguide. Single-mode out coming signal is obtained by an infrared camera.