What are Fabry-Perot (FP) laser diodes?
A Fabry-Perot (FP) laser diode is a type of laser diode that has two broad-band optical mirrors at either end of the diode which forms an optical cavity. The FP laser diode uses AlGaAs, InGaAsP, AlGaInP, etc as the gain medium. Fabry-Perot laser diodes are available as free-space and fiber-coupled types. FP laser diodes are usually available in the C-mount, TO-Can, TO-Can pigtailed, HHL, Butterfly, module, chip, DIL, Die, D-mount, CS-mount, and F-mount packages. The FP laser diodes are ideal for defense, industrial, communications, Ethernet, PON, and SDH applications.
The reflector at the back of the diode has high-reflectivity and the reflector at the front has low reflectivity. GaAs is usually used to form the PN-junction of the diode. When the diode is forward biased, electron-hole recombinations occur and it results in photon release. Now, the emitted photons start bouncing between the mirrors which will lead to more recombinations and release more photons. The light bounces between these reflectors to form standing waves or longitudinal modes, which are then emitted out of the diode.
Key Specifications of Fabry-Perot(FP) laser diodes:
Central wavelength: Represents the wavelength of laser emitted from the diode. The wavelength is usually represented in nm (nanometre). The Fabry-Perot laser diode can have a wavelength range of 379nm to 1610nm. Higher wavelength diodes are also available.
Type: Free space/Fiber-coupled
Operation mode: Continuous wave/Pulsed laser
Technology: Fabry-Perot laser (FP)
Spectral width (FWHM): It is the width of the optical spectrum at the half-maximum power. It is represented in nanometre.
Output power: Represents the output power of the Fabry-Perot laser diode. Fabry-Perot laser diodes are available in various power ranges. Mostly, the output power range is 2 mW to 1W.
Longitudinal mode: single-mode/Multi-mode
Threshold current (Ith): It is the current at which the output optical power increases sharply. When the laser diode is biased below this threshold current, the output optical power will be very low. Usually, the threshold current of Fabry-Perot laser diode can have range from 10mA to hundreds of milli Amps.
Working current: It is the driving current or input currents when the Fabry-Perot laser diode reaches the rated power. Typically, it is in the range of 27mA to 1.93A.
Operating voltage: Represents the supply voltage. Normally, Fabry-Perot diodes have a 1.1V to 2V range.
Reverse voltage: It represents the maximum allowable reverse voltage, when it is applied across the laser diode. Beyond the reverse voltage, the diode will damage. It is usually in the range of 2 V.
Vertical Divergence Angle (θ⊥): The angle at which the light-emitting band spreads in a direction vertical to the PN junction.
Horizontal Divergence Angle (θ∥): The angle at which the light-emitting band spreads in a direction parallel to the PN junction.
Operating temperature: Represents the safe operating temperature of the laser diode. Typically, it has a range of -40 °C to +85°C.
Storage temperature: Represents the storage temperature range of laser diode. Typically, it has a range of -40 °C to +85°C.
Package type: Represents the type of package used to pack the laser diode. Usually, the Fabry-Perot laser diodes are available in the C-mount, TO- Can, TO-Can pigtailed, HHL, Butterfly, module, chip, DIL, Die, D-mount, CS-mount, and F-mount packages.