What is a DBR laser diode?
DBR laser diode structure
Fiber coupled DBR laser diode (Butterfly package)
DBR or distributed-Bragg-reflector (DBR) laser diode is a type of single frequency laser diode. They operate at a wavelength from 783 to 1083 nm and are available in both free-space and fiber-coupled configurations. The output power of the DBR laser diodes varies in the mW range. The output wavelength of the DBR laser diode is continually tunable and can be varied by varying the current or temperature. The DBR laser diodes are noise-free optical sources. While operating with a low noise power supply at a constant temperature, it provides a line width of less than 10 MHz. The DBR laser diodes are available in the butterfly (BTF), TO-Can, sub-mount, and C-mount packages. These diodes are ideal for spectroscopy, time-resolved fluorescence, medical diagnostics, metrology, and solid-state pumping applications.
The resonant cavity of this diode consists of a reflector at one end of the diode (Grating region) and a low reflective cleaved exit facet on the opposite end. The active or gain region of the diode is available between these two reflective ends. The ridge width of the DBR laser diode is very narrow, typically in the micron range. Also, the DBR mirror or grating feedback is designed to reflect the single longitudinal mode. Hence, the DBR laser diodes emit the laser light with a single-mode or single-frequency.
Specifications of DBR laser diode:
Central wavelength: Represents the wavelength of laser emitted from the DBR laser diode. The wavelength is represented in nm (nanometre). A DBR laser diode can have a wavelength range of 783nm to 1083nm.
Type: Free space/ Fiber coupled. A free space DBR laser diode emits the laser light in free space, and a fiber coupled DBR laser diode emits light through the fiber optic medium.
Spectral width (FWHM): It is the width of the optical spectrum at the half-maximum power. Usually, the spectral width of DBR laser diodes can vary from 0.7 to 10 MHz.
Output power: Represents the output power of the laser diode. A DBR output power is in the range of milliwatts.
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 a DBR laser diode can vary from 30mA - 80mA (or) in-between this range.
Working current: It is the driving current or input currents when the laser diode reaches the rated power. Usually, the operating current of a DBR laser diode can from 20mA to 0.5 A.
Operating voltage: Represents the supply voltage. Normally, a DBR diode can have the operating voltage range of 2V to 2.5V (or) 2V to 4V.
Reverse voltage: Represents the maximum allowable reverse voltage, when it is applied across the laser diode. Beyond the reverse voltage, the diode will damage. Usually the reverse voltage of a DBR laser diode is 2V or 2.5 V.
Vertical Divergence Angle (θ⊥): The angle at which the light-emitting band spreads in a direction vertical to the PN junction. It is usually in the range of 15˚-40˚.
Horizontal Divergence Angle (θ∥): The angle at which the light-emitting band spreads in a direction parallel to the PN junction. Typically, it is in the range of 6˚-10˚.
Operating temperature: Represents the safe operating temperature of the DBR laser diode. Typically, it has a range of -40 °C to +85°C.
Storage temperature: Represents the storage temperature range of DBR laser diode. Typically, it has a range of -45 °C to +80°C.
Package type: Represents the type package used in the DBR laser diode. Usually, the DBR laser diodes are available in the Butterfly (BTF) , TO-Can, Sub-mount, and C-mount packages.