to get the laser threshold power Ith

work in the saturated zone (Note: Any semiconductor laser will have a current limit protection and laser life from consideration, the circuit design flow point of time will be less than the current limit of 20 ~ 40%). the working status of digital signal transmission, in a graph, we can see, the minimum input current when the output is still light, but in the digital circuit, if the "0" data is still light out, then determine the "1" and "0", it may be introduced or false (technically known as error, see selected as part of - part of the next page in bold). Many products of  laser pointer  adopt the 2.4G technology of laser pointer .
Therefore, the working status of digital circuit is "0" is located at near (mainly consider the following aspects: near the threshold value can greatly reduce the lightning delay, relaxation oscillation while a certain degree of inhibition; smaller modulation current can be enough output optical pulse, which can reduce the pattern effect and heating effect results; low extinction ratio can be a small error rate;, etc.). Direct modulation bandwidth: because the junction capacitance characteristics of semiconductor lasers, and can not be drawn like the diagram above as the ideal work for different input laser frequency, the response is not the same, generally the higher the frequency, the amplitude of the output optical system, the smaller the stress . Semiconductor laser bandwidth is defined as the amplitude of the input signal under the same conditions, the output light intensity is low-frequency modulation amplitude modulation 1 / 2 frequency, (now the most high-speed modulation is 10GHz bandwidth, but the PN used in our experiment the larger end, so that the bandwidth of 15KHz or so). The 2.4G technology of laser pointer  is the selling point of  laser pointer .
The operating point knob counter-clockwise head (the operating point adjustment knob clockwise, counterclockwise gently about, you can determine by feel whether, careful not to strong hard-line knob.) Turn the power semiconductor laser demonstrator; by modulation options button (twice within the default boot modulation), the semiconductor laser to adjust to continuous state; clockwise adjustment of electricity, more than one state record voltage, current and power value. Through mapping, to get the laser threshold power Ith.