Chen Gen-xiang

Design of Phosphor-Free Single-Chip White Light-Emitting Diodes Using InAlGaN Irregular Multiple Quantum Well Structures

A novel approach for the design of phosphor-free single-chip white light-emitting diodes (LEDs) is proposed by employing InAlGaN irregular multiple quantum well (IMQW) structures. The electronic and optical properties of the designed InAlGaN IMQWs are analyzed in detail by fully considering the effects of strain, well-coupling, valence band-mixing, and quasi-bound states using the effective-mass Hamiltonian deduced from k ? p theory. For comparison, three different types of InAlGaN IMQW structures with ultra-wide band spontaneous emission spectra are analyzed, and the results show that phosphor-free single-chip white light LEDs with more than 200 nm emission band can be obtained using properly designed InAlGaN IMQW structures.

An Advanced Dynamic Model for Semiconductor Optical Amplifiers and Laser Diodes

We propose a unified time-domain dynamic model for both semiconductor optical amplifiers and laser diodes by employing a set of multi-longitudinal-mode coupled wave rate equations. A novel split-step method has been developed for the numerical solution of the equation set. To demonstrate the capabilities of the model, some calculation results for conventional and distribute feedback-type gain-clamped semiconductor optical amplifiers are presented.

Erbium Doped Fiber Amplifier Gain Flattening Using Long-Period Fiber Gratings

Based on theoretical and experimental studies on the optical properties of long-period gratings (LPGs), an erbium doped fiber amplifier (EDFA) gain equalizer was fabricated by writing three long period gratings with designed properties in hydrogen-loaded standard single-mode fibers. The LPGs were written by a KrF excimer laser at 248 nm with amplitude masks. The gain variation of ±3 dB in the EDFA is reduced to ±0.3 dB with a bandwidth of 30 nm and the total insertion loss of the device is less than 0.3 dB.

Optimization of a GaN-based irregular multiple quantum well structure for a dichromatic white LED

GaN-based irregular multiple quantum well (IMQW) structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes (LEDs) are optimized in order to obtain near white light emissions. The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain, well-coupling, valence band-mixing and polarization effect through employing a newly developed theoretical model from the k p theory. Several structure parameters such as well material component, well width, layout of the wells and the thickness of barrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure. Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two, the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness. The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.

EDFA gain spectrum flattening based on long period fiber grating

In this paper, for the first time to our knowledge, we have performed EDFA gain spectrum flattening effectively based on a long period fiber grating (LPG), which has been fabricated by the moving fiber/phase mask-scanning beam technique. The results show the flat bandwidth of the related EDFA exceeding 30 nm and the fluctuation is less than 0.6 dB.