Yejin Zhang

Design and Analysis of Laser Diodes Based on the Longitudinal Photonic Band Crystal Concept for High Power and Narrow Vertical Divergence

High-power low-vertical-divergence laser diodes based on the longitudinal photonic band crystal (PBC) concept are investigated at a wavelength of 900 nm. The thicknesses of the layers in the longitudinal PBC waveguide are prudently optimized by mode analysis, and the lowest vertical far-field angle is found to be achieved by mode coupling. A self-consistent model is also utilized to study the device performances in detail, which shows excellent optical properties without obvious electronic performance degradation. In the experiment, continuous wave power up to 1 W/facet and vertical far-field angles of less than 10° (full-width at half-maximum) and ~50° (with 95% power content) are achieved simultaneously, with epitaxial wafer containing PBC layers of ten periods. The agreement among the design, simulation, and experiment shows a bright prospect for further reduced vertical divergence angle with high power output.

A hybrid silicon single mode laser with a slotted feedback structure

In this paper, a III-V/Silicon hybrid single mode laser operating at a long wavelength for photonic integration circuit is presented. The InGaAlAs gain structure is bonded onto a patterned silicon-on insulator wafer directly. The novel mode selected mechanism based on a slotted silicon waveguide is applied, which only need standard photolithography in the whole technological process. The side mode suppression ratio of larger than 20dB is obtained from experiments.

Hybrid III–V-silicon single-mode laser with periodic microstructures

In this Letter, a III-V/silicon hybrid single-mode laser operating at C band for photonic integration circuit is presented. The InGaAlAs gain structure is bonded onto a patterned silicon-on insulator through wafer to wafer directly. The mode selected mechanism based on a hybrid III-V/silicon straight cavity with periodic microstructures is applied, which only need low cost i-line projection photolithography in the whole technological process. At room temperature, we obtain 0.62 mW output power in continuous-wave. The side mode suppression ratio of larger than 20 dB is obtained from experiments. [corrected].

Slotted Hybrid III–V/Silicon Single-Mode Laser

In this letter, a III–V/silicon hybrid single-mode laser operating at L band for photonic integrated circuits is presented. The AlGaInAs gain structure is bonded onto a patterned silicon-on insulator wafer directly. The novel mode-selection mechanism based on a slotted silicon waveguide is applied, which only needs i-line projection photolithography in the whole fabrication process. At room temperature, we obtain 0.85 and 3.5 mW output power in continuous-wave and pulse-wave regimes, respectively. The side-mode suppression ratio of larger than 25 dB is obtained from experiments.

The impact of imperfect symmetry on band edge modes of a two-dimensional photonic crystal with square lattice

A theoretical analysis has been performed by means of the plane-wave expansion method to examine the dispersion properties of photons at high symmetry points of an InP based two-dimensional photonic crystal with square lattice. The Q factors are compared qualitatively. The mechanism of surface-emitting is due to the photon manipulation by periodic dielectric materials in terms of Bragg diffraction. A surface-emitting photonic crystal resonator is designed based on the phenomenon of slow light. Photonic crystal slabs with different unit cells are utilized in the simulation. The results indicate that the change of the air holes can affect the polarization property of the modes. So we can find a way to improve the polarization by reducing the symmetry of the structure.

High-brightness diode laser arrays integrated with a phase shifter designed for single-lobe far-field pattern.

High-brightness 910 nm wavelength edge-emitting laser arrays integrated with a phase-shifter have been designed. Over 450 mW/facet with M2 <; 3 is achieved experimentally. Such devices show bright future for low cost and easy fabrication.

500-mW CW Single-Lobe Emission From Laterally Coupled Photonic Crystal Laser Arrays

Edge-emitting laser arrays based on the laterally coupled photonic band crystal (PBC) concept have been designed and fabricated at a wavelength of 925 nm. Multiple ridge lasers are pumped and coherently coupled, and several narrow passive stripes are distributed on both sides acting as PBC. Compared to the localized fundamental supermode, high-order supermodes expand over the lateral PBC region and are suppressed. Thus, stable fundamental supermode operation and narrow far-field divergence are easily obtained. For a cavity length of 500 μm, an output power of more than 500 mW/facet in continuous wave operation and a far-field divergence angle of nearly 10° (full width at half maximum) in the slow axis are achieved.

Design of Photonic Crystal Semiconductor Optical Amplifier With Polarization Independence

Slow-light effects in photonic crystal (PC) waveguides can enhance light-mater interaction near the photonic band edge, which can be used to design a short cavity length semiconductor optical amplifier (SOA). In this paper, a novel SOA based on slow-light effects in PC waveguides (PCSOA) is presented. To realize the amplification of the optical signal with polarization independence, a PCSOA is designed with a compensated structure. The cascaded structure leads to a balanced amplification to the TE and TM polarized light.

Spontaneous-emission control by local density of states of photonic crystal cavity

The local density of states (LDOS) of two-dimensional square lattice photonic crystal (PhC) defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point off the centre (for example, at the point (0.3a, 0.4a), where a is the lattice constant) is extremely enhanced. Further, the disordered radii are introduced to imitate the real devices fabricated in our experiment, and then we study the LDOS of PhC cavity with configurations of different disordered radii. The results show that in the disordered cavity, the LDOS in the centre is still greatly reduced, while the LDOS at the point (0.3a, 0.4a) is still extremely enhanced. It shows that the LDOS analysis is useful. When a laser is designed on the basis of the square lattice PhC rod cavity, in order to enhance the spontaneous emission, the active materials should not be inserted in the centre of the cavity, but located at positions off the centre. So LDOS method gives a guide to design the positions of the active materials (quantum dots) in the lasers.

High-Performance Low-Divergence Angled Laser Diodes With Two-Dimensionally Tilted Sidewalls

High-performance low-divergence angled laser diodes are proposed and fabricated at a wavelength of 910 nm. Light is reflected both inward to the waveguide and downward to the lower cladding layer by the 2-D tilted sidewalls along its zigzag path in the waveguide, and thus the mode field is extended and the transverse divergence angle is greatly reduced. Experimentally, reduced transverse divergence angles by over 20° are demonstrated in both pulse and continuous wave modes, and stable and narrow lateral divergence angles are simultaneously achieved. This device shows a promising future for improving the transverse far-field pattern by surface structure with easy fabrication.