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Second, optoelectronic components and characteristics
According to the outside optoelectronics manufacturing optoelectronic devices have photoelectron, inflatable phototubes and photoelectric times once tube.
1. Phototubes phototubes are various and typical products are vacuum phototubes and inflatable phototubes, light its appearance and structure as shown in figure 1 shows, made of cylindrical metal half cathodic K and is located in the wires cathodic axis of anode in A package of smoke into the vacuum, when incident light within glass shell in the cathode, illuminate A single photon took all of its energy transfer to the cathode materials A free electrons, so as to make the freedom electronic energy increase h. When electrons gain energy more than escape of cathode materials, it reactive A metal surface constraints can overcome escape, form electron emission. This kind of electronic called optoelectronics, optoelectronic escaping the metal surface for after initial kinetic energy
Phototubes normal work, anode potential than the cathode, shown in figure 2. In one shot more than "red light frequency is premise, escape from the optoelectronic cathode surface by positive potential attracted the anode in photoelectric tube forming space, called the current stream. Then if light intensity increases, the number of photons bombarded the cathode multiplied, unit of time to launch photoelectron number are also increasing, photo-current greatens. In figure 2 shows circuit, current and resistance is the voltage drop across the only a function of light intensity relations, so as to achieve a photoelectric conversion. When the LTT optoelectronic cathode K, electronic escape from the cathode surface, and was the photoelectric anode is an electric current, power plants absorb deoxidization device in the load resistance - I, the voltage
Phototubes photoelectric characteristics fig.03 shows, from the graph in flux knowable, not too big, photoelectric basic characteristics is a straight line.
2. Photoelectric times had the sensitivity of vacuum tube due to low, so with people developed has magnified the photomultiplier tubes photo-current ability. Figure 4 is photomultiplier tube structure schematic drawing.
光电倍增结构示意图
From the graph can see photomultiplier tubes also have A cathode K and an anode A, and phototubes different is in its between anode and cathode set up several secondary emission electrodes, D1, D2 and D3... They called the first multiply electrode, the second multiply electrode,... Usually, double electrode for 10 ~ 15 levels. Photomultiplier tubes work between adjacent electrode, keeping a certain minimum, including the cathode potential potentials, each multiply electrode potential filtering increases, the anode potential supreme. When the incident light irradiation, cathodic K escape from the optoelectronic cathode multiplied by first accelerated, by high speed electrode D1 bombarded caused secondary electron emission, D1, an incident can generate multiple secondary electron photonics, D1 emit of secondary electron was D1, D2 asked electric field acceleration, converged on D2 and again produce secondary electron emission... So gradually produce secondary electron emission, make electronic increased rapidly, these electronic finally arrived at the anode, form a larger anode current. If a n level, multiply electrodes at all levels for sigma, the multiplication of rate is the multiplication of photomultiplier tubes can be considered sigma n rate, therefore, photomultiplier tube has high sensitivity. In the output current is less than 1mA circumstances, it in a very wide photoelectric properties within the scope of the linear relationship with good. Photomultiplier tubes this characteristic, make it more for light measurement.
3 and photoconductive resistance photoconductive resistance within the working principle is based on the photoelectric effect. In semiconductor photosensitive material ends of mount electrode lead, it contains transparent window sealed in the tube and shell element photoconductive resistance. Photoconductive resistance properties and parameters are: