Interest in Quantum Dot Lasers stem mainly from the low threshold current which can result due to quantization of energy levels and change in density of state function. In the most commonly used laser separate confinement heterostructures, the nanoscale active region is “built into” the waveguide region (optical confinement layer, OCL) based on a wide gap semiconductor material.The most important characteristic of quantum dot laser is the amount of light it emits as current is injected into device. The dependence of laser power output (P) on current (I), cavity length and various other parameters has been estimated on the basis of rate equations model. Linear relation has been obtained between P and I and as the cavity length increases, slope of P-I characteristic decreases.The external quantum efficiency indicates the efficiency of a laser device in converting the injected electron-hole pairs (input electric charges) to photons emitted from the device (output light). External differential quantum efficiency decreases linearly with increasing cavity length. As the internal loss increases, the slope of external differential quantum efficiency versus cavity length decreases. The internal quantum efficiency is independent of the geometrical properties of the laser device, such as the cavity length or the stripe width. Internal quantum efficiency is one of the main Figures of merit that should be used in assessing the quality of the semiconductor wafer from which the quantum dot laser is manufactured from.One of the most important device characteristics of a laser diode is the efficiency of conversion ????c of the input electric power into output optical power P. Power conversion efficiency is found to increase with increasing drive current, gets its maximum value and after that it decreases slightly with increasing drive current. Power conversion efficiency also depends on different parameters like cavity length, internal efficiency, threshold current.
Audience Take Away Notes :
- This work will help to understand how various parameters affect the light output obtained from quantum dot lasers.
- This will help the audience to decide which material and of what size, should be used to get laser of required power with higher efficiency.
- This could be used by other faculty to expand their research or teachings by taking other parameters also into consideration which may suggest even better performance of the device.
- This suggests how to reduce the threshold current for a diode laser by using quantum dots of different semiconductors