Introduction:
laser pens, laser torches, laser printers and other laser products are indispensable to the existence of
laser diode, laser diode is how it works?
What is the difference with the ordinary photodiode?
The next question is revealed。
Laser diode principle - about lasers
The first thing to know about laser diodes is to understand the stimulated radiation. There are three kinds of radiation in the radiation,
Ⅰ: in the high energy particles spontaneously to the low-energy state transition, called the spontaneous radiation;
Ⅱ: it is in the high energy particles under the excitation of external light to the low-energy state transition, called the stimulated radiation;
Ⅲ: it is in a state of particles absorb foreign to the upper state transition is called stimulated absorption of light energy.
Spontaneous radiation, even the two at the same time from a high-energy state to the low-energy state transition of particle, phase, polarization state, they emit light emission direction may also be different, but stimulated radiation is different, when the upper state of particles under the excitation of external photon to the low-energy state transition, issued in terms of frequency, phase, polarization state and foreign same photons of light.
In the laser, the radiation that occurs is stimulated radiation, and the laser emitted is identical in frequency, phase, polarization state, etc.
In any stimulated optical system, there is stimulated radiation and stimulated absorption. Only if the stimulated radiation is dominant, the external light can be amplified and the laser is emitted. And are in general illuminant stimulated absorption edge, only the particle equilibrium is broken, the high energy particle number is greater than the low-energy state of particle number (it is called ion inversion), can a laser.
Laser diode principle - structure
Physical structure of laser diode is in the light emitting diode junction placed a layer of light between the activity of semiconductor and its end after polishing has partially reflecting function, thus forming an optical resonator.
In the case of positive bias, LED DE facto radiates light to and interact with optical cavity, thus further incentives single wavelength of light that is emitted from the junction physical properties related to the material of this kind of light.