The infrared technology of green laser pointer can be enhanced more

The infrared technology of green laser pointer can be enhanced more.
Threshold effects of several factors: the greater the concentration of doped crystals, the smaller the threshold value. Cavity loss, such as increasing the reflectivity, the threshold is low. Junction with the semiconductor materials, heterojunction threshold current is much lower than the homojunction. Currently, the room temperature threshold current of homojunction than 30000A/cm2; single heterojunction about 8000A/cm2; double heterojunction about 1600A/cm2. Now been made of double-heterostructure at room temperature to tens of milliwatts of continuous output semiconductor laser. The higher the temperature, the higher threshold. Above 100K, the threshold increases with the cube of T. Therefore, the semiconductor laser is best to work at low temperature and room temperature. Threshold current (Ith) of measurement methods. In Figure 19.4 shows the typical features of a typical diagram of the semiconductor laser in which the curve is the output optical power and current relationship (solid line), dashed line is the relationship between power and current results of a derivative, is crossed power and current of the second derivative of the curve results. General description of the threshold value of several commonly used with the following process: a, the rapid increase in the PI curve to take off on one of the linear part of the extension line and the abscissa of the intersection; b, part of the fluorescence and laser parts, respectively, look similar to into two lines, then the intersection of two lines is the threshold value; c, the curve in dP-dI, the rising delay to take the midpoint (10% and 90% points of the mid-point); d, d2P/dI2 of vertex as the threshold point. The infrared technology ofgreen laser pointer is the key point.
As the short cavity semiconductor lasers, laser direction is poor, in the end of the vertical plane, the maximum divergence angle, up to 20 ° -30 °; at the end of the horizontal plane is about 10 ° or so. (Because the experiments, we used LD is already collimated LD, so do not arrange this part of the experiment). Semiconductor lasers based on the work of V-I curve, semiconductor lasers can be obtained within the other two important parameters: cut-off voltage and series resistor. We all know that semiconductor lasers operating voltage is constant, while the V-I work there is a certain slope of the curve, which is the laser series resistance inherent in the decision, it produces power primarily in the form of heat release. Seen as a quality laser parameters, the series resistance should be as small as possible. Reverse curve to extend the V-I axis intersects with the laser can be cut-off voltage (Vj), with threshold current (Ith) the, Ith, the lower, the better the performance. Which Pex is the laser output optical power, h is Planck's constant, e0 is the electron charge constant, I is current. When the general 77K, GaAs laser external quantum efficiency of 70% -80%; 300K, the reduced 30%.