1.5um InGaAsP / InP Quantum Well Laser Structure
Using bulk materials and quantum wells as active regions, InP-based material systems can cover all wavelengths of optical fiber communication. At present, materials used in optical communication are mainly concentrated in InGaAsP and GaAlInAs systems based on InP. Among them, InGaAsP / InP quantum well material has high crystal symmetry and large saturated electron drift rate. Its electrical properties can be changed by applying an electric field. It has great advantages in the application of semiconductor optoelectronic devices. The high-power 1.5um communication band quantum well semiconductor laser can be used in space laser communication, laser radar, laser guidance, etc. Ganwafer is able to manufacture laser diode wafers to meet your devices’ demands, additional wafer information please visit https://www.ganwafer.com/product/iii-v-epi-wafer/. Here we take the 1.5um InGaAsP quantum well laser heterostructure for example:
1. InGaAsP / InP Quantum Well Laser Structure
PAMP18047 – 1500LD
|7||p-InGaAs top contact||100nm||–||Ohmic contact|
|6||p-InP top cladding||–||5E17cm-3||–|
|5||1.15Q InGaAsP SCH||–||–||–|
|4||InGaAsP QW x**pairs||–||–||–|
|3||1.15Q InGaAsP barrier x**pairs
+1% compressive strain
|2||1.15Q InGaAsP SCH||200nm||–||–|
PL wavelength: ~1.50um
The quaternary material InGaAsP is used as the barrier material to reduce the barrier height and form the carrier limit with appropriate barrier height. At the same time, a symmetrical passive waveguide layer of quaternary material is grown on the top and bottom of the active area of the quantum well to increase the optical limiting factor, and the optical limiting is formed by the up and down InP with low refractive index. The threshold current density can be greatly reduced by the structure of the separately confined strained layer quantum well laser.
2. How to Improve the Light Output Power of Quantum Well based Laser Diode?
So far, the two main factors affecting the improvement of output power are electro-optical conversion efficiency (slope efficiency) and catastrophic optical damage (COC). The slope efficiency of laser is determined by its internal quantum efficiency, internal loss and cavity length. To obtain quantum well based lasers with high output power, we give you several suggestions from reducing the internal loss.
For the internal loss of the multiple quantum well laser, its main mechanism is caused by carrier absorption inside the material, waveguide scattering loss, uneven epitaxial quality or optical scattering caused by material defects. The quality of epitaxial laser wafers directly affects the size of internal loss. For devices, free carrier absorption from the active region and high doped limit layer, as well as a small part of scattering loss from the waveguide structure. Therefore, on the premise of ensuring the epitaxial quality of the material, the internal loss of the waveguide can be reduced by reasonably designing the optical field distribution in the optical cavity and the doping morphology of the quantum well laser material.
The total loss caused by free carrier absorption is determined by the limiting factor of each layer, the concentration of electrons and holes, and the scattering cross section. Therefore, we can take following means to reduce the internal total loss:
1) Reduce the doping concentration of the waveguide layer and the limiting layer of laser epitaxy to reduce the carrier concentration;
2) Reduce the optical limiting factor of the quantum well layer;
3) Since the scattering cross section of the hole is larger than that of the electron, it need to reduce the limiting factor of the p-type cladding by introducing an asymmetric waveguide to transfer the light field to the n-region.