Commonly used laser diode
①PIN photodiode. When it receives light power to generate photocurrent, it will bring quantum noise.
②Avalanche photodiode. It can provide internal amplification, which has a longer transmission distance than PIN photodiodes, but has greater quantum noise. In order to obtain a good signal-to-noise ratio, a low-noise pre-amplifier and a main amplifier must be connected behind the optical detection device.
Common parameters of semiconductor laser diodes
(1) Wavelength: the working wavelength of the laser tube. The current laser tube wavelengths that can be used as photoelectric switches are 635nm, 650nm, 670nm, 690nm, 780nm, 810nm, 860nm, 980nm, etc.
(2) Threshold current Ith: the current at which the laser tube starts to generate laser oscillation. For general low-power laser tubes, its value is about tens of milliamps. The threshold current of a laser tube with a strained multiple quantum well structure can be as low as 10mA. the following.
(3) Operating current Iop: the drive current when the laser tube reaches the rated output power. This value is more important for designing and debugging the laser drive circuit.
(4) Vertical divergence angle θ⊥: The angle at which the light-emitting band of the laser diode opens in the vertical direction of the PN junction, generally around 15 to 40.
(5) Horizontal divergence angle θ∥: The angle at which the light-emitting band of the laser diode is opened in the direction parallel to the PN junction, generally around 6-10.
(6) Monitoring current Im: the current flowing through the PIN tube when the laser tube is at the rated output power.
Laser diodes have been widely used in low-power optoelectronic devices such as optical disc drives in computers, print heads in laser printers, barcode scanners, laser distance measurement, laser medical treatment, optical communications, laser instructions, etc., in stage lighting, laser surgery It has also been used in high-power equipment such as laser welding and laser weapons.