What are Multi-mode laser diodes?
Multi-mode laser diode with a flat pack
Understanding multi-mode outputs
Understanding single-mode outputs
A multi-mode laser diode is a type of laser diode that produces light pulses which have various modes of propagation. These diodes are ideal for the applications, such as laser cladding, surface-enhanced Raman spectroscopy (SERS), laser pumping, and machine vision.
Ridge width (100 microns)
The type of material and their compositions used in the fabrication of the multi-mode laser diode decides the wavelength of light. When the ridge width of a laser diode is more than the wavelength of the light, then the laser diode can operate in multiple transverse optical modes. A multi-mode laser diode emits the laser beam with multi kinds of transverse resonator modes. Usually, the ridge width of a multi-mode diode is in the range of 100 microns that results in a recombination process of holes and electrons and generates the laser light with high power. Additionally, because of the more width, the surface area of the facet is larger, which reduces both the intensity and risk of catastrophic optical damage.
Key Specifications of a multi-mode laser diode:
Central wavelength: Represents the wavelength of laser emitted from the diode. The wavelength is represented in nm (nanometre). The multi-mode laser diode can have a wavelength range of 445nm to 1850nm.
Output power: Represents the output power of the multi-mode laser diode. Multi-mode laser diodes are available in various power ranges. Typically, 200 mW to several KW.
Longitudinal 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. It is represented in XmA.
Working current: It is the driving current or input currents when the multi-mode laser diode reaches the rated power. It is represented in XmA.
Operating voltage: Represents the supply voltage. Normally, it has a 4.5V to 5V range.
Reverse voltage: 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 2V to 5V.
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 laser diode. Typically, it has a range of -10 °C to +70°C.
Storage temperature: Represents the storage temperature range of laser diode. Typically, it has a range of -45 °C to +85°C.
Package type: Represents the type package used to pack the laser diode. Usually, the multi-mode laser diodes are available in the C-mount package, TO- Can package, Flatpack, TO-with thread package, and integrated FAC/SAC package.