The selling point of green laser pointer

2.4G technology of green laser pointer  is more popular. Divided into pulse amplitude modulation pulse modulation (PAM), pulse intensity modulation (PIM), pulse frequency modulation (PFM), pulse-position (PPM) and pulse width modulated (PWM) and other types. Pulse Code Modulation (PCM) is a continuous analog signal by the first sampling, quantization and coding, into a binary pulse code, amplitude and width of the rectangular pulse are equal, no to that, then this series reflect the digital signal regular electrical pulses applied to one modulator to control the laser output. This form is also known as digital modulation intensity modulation (PCM / IM). Indirect load modulation signal modulation is carried out after the formation of the laser, ie modulator placed outside the laser resonator, the modulator modulating signal voltage on the increase, so that certain physical characteristics of the modulator phase change occurred, when the laser through the it is to be modulated. The 2.4G technology of led flash light is more widely used.
So externally modulated laser parameters are not changed, but the change has been the output of the laser parameters (intensity, frequency, etc.). Since the introduction of modulation in the wavelength chirp, so that people outside of the current modulation is a modulation method more attention. Indirect method of laser modulation by the modulator is based on different principles often divided into electro-optic modulators, acousto-optic modulator, magneto-optical modulation, interference modulation. Direct modulation is the modulation signal in the load during the process of laser oscillation, the modulation signal to change the laws of the oscillation parameters, the laser output characteristics to achieve the change aims to achieve modulation. For example, by directly controlling the output of the laser pump source to modulate the laser intensity. Modulation within the laser cavity can also be placed in the modulation component, with the modulation signal control devices, to change the parameters of the cavity, thereby changing the laser output characteristics to achieve modulation. Direct modulation of the basic institutions such as the right. As direct modulation techniques with a simple, economic, easy to implement, etc., is the most commonly used low-speed optical fiber communication modulation, but only suitable for semiconductor lasers and light emitting diodes, because semiconductor lasers and light emitting diode (the laser is , above some threshold) is basically proportional to the injected current, and the current change is converted to optical frequency modulation is linear, so it can be achieved by changing the injection current to the light intensity modulation. The manager says that the 2.4G technology of green laser pointer  is more practical in use.
Directly modulated light sources will be introduced to chirp, this system will be introduced in long-distance large dispersion, the transmission quality deterioration, especially in high-speed transmission systems, should be avoided. The figure shows the light intensity modulation direct schematic diagram, in which the vertical axis of the semiconductor laser output power, the abscissa of the semiconductor laser operating current, following the curve of each graph is modulated current signal, the right is the modulated optical input current signal. (A), analog signal transmission is normal working condition, can be seen from the figure the input signal and output signal distortion is small, note that the basic state of the operating point in the linear region of the mid-point. (B), is at work in the area of the properties, as a result of low power, so there are a large part of the signal distortion, resulting in signal distortion. (C) 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%). (D), 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  green laser pointer  adopt the 2.4G technology of green 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 green laser pointer  is the selling point of  green 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. The use of data obtained from 5 to calculate the series resistance, power efficiency and external differential quantum efficiency (approximately equal to one wavelength of 670nm). The 2.4G technology of green laser pointer  is advanced enough.