What are Fiber Coupled Laser Diodes?
Fiber-coupled laser diode (Coaxial package)
A fiber-coupled laser diode, a laser diode coupled with a fiber optic cable. The fiber optic cable is used to deliver the light to other optical components. These diodes are ideal for applications, such as medical treatment, laser pumping, material dealing, and heating, printing, aiming beam, and communication.
Advantages of fiber-coupled laser diode:
- They emit a smooth (homogenized), symmetric, high quality laser beam which is needed for many applications.
- The fiber-coupled laser diode can easily be coupled with the other optical components.
Single-mode fiber-coupled laser diodes
https://www.youtube.com/watch?v=45X0puB3YK0
Single-mode
Single-mode beam output
A single-mode fiber-coupled laser diode operates in a single transverse resonator mode, which is the Gaussian mode. Usually, the ridge width of the single-mode fiber-coupled laser diode is very small, 3 to 10 microns wide. Hence, this type of laser diodes emits laser with low power, usually is in the range of 1 mW to 1.5 W. The diameter of the fiber core of a single-mode fiber-coupled laser diode is small, typically 6 to 9 μm. Because of the smaller diameter, this type of diode emits a light beam with only one mode of propagation, and it is possible to focus the laser light at one spot by using a lens or a microscope. The butterfly package, DIL package, and Coax package are the most used package to assemble these types of laser diodes.
Multi-mode fiber-coupled laser diodes
https://www.youtube.com/watch?v=uzXLhTW9wWQ
Multi-mode
Multi-mode beam output
A multi-mode fiber-coupled laser diode emits the laser beam with multiple transverse resonator modes. They have a core diameter which usually measures 62, 100, 200, 400, 800, and 1000 μm (can go even higher). The typical ridge width range of a multi-mode fiber-coupled diode is in the range of 100 microns, which results in the recombination process of holes and electrons. This generates a high power laser light. The large diameter of the fiber core allows the multi-mode propagation through the fiber optic cable. Due to multiple dispersion, the attenuation of the signal in multi-mode is higher than the single-mode laser diode. These diodes are suitable for applications, such as laser pumping, printing, material dealing, and heating.
Key Specifications of fiber-coupled laser diodes:
Central wavelength: Represents the wavelength of laser emitted from the fiber-coupled laser diode. The wavelength is represented in nm (nanometre). Both the single-mode fiber-coupled laser diode and multi-mode fiber-coupled laser diode can have a wavelength range of 405 to 1610 nm.
Output power: Represents the output power of the fiber-coupled laser diode. The single-mode fiber-coupled laser diodes are available in the power range of 1 mW to 1.5 W. Similarly, the Multi-mode fiber-coupled laser diodes are available in various power ranges. Typically, 200 mW to several KW.
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. It is represented in X mA. The threshold current is proportional to the output power.
Operating current: It is the driving current or input currents when the multi-mode laser diode reaches the rated power. It is represented in X mA. The operating current is proportional to the output power.
Operating voltage: Represents the supply voltage. Normally, it has a 4.5 to 5 V range. The operating voltage is proportional to the output power.
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 2 to 5 V.
Fiber core size: Typically, For single mode, the fiber core diameter varies from 6μm to 9μm, and for muti-mode, it has a range of 62, 100, 200, 400, 800, or even > 1000 μm.
Fiber length: Typically, For single mode, the fiber length varies from 3μm to 9μm, and for muti-mode, it has a range of 50 μm to 1000 μm.
Fiber connector: Represents the type of fiber connector used with the fiber-coupled laser diode. Usually, these types of laser diodes are available with FC or ST or SMA905 or FC/PC connectors.
Operating temperature: Represents the safe operating temperature of the fiber-coupled laser diode. Typically, it has a range of -10 °C to + 70 °C.
Storage temperature: Represents the storage temperature range of fiber-coupled laser diode. Typically, it has a range of -35 °C to + 85 °C.
Package type: Represents the type package used to pack the fiber-coupled laser diode. Usually, the single-mode fiber-coupled laser diodes are available in the coaxial package, butterfly package, and the DIP package, and the multi-mode fiber-coupled laser diodes are available in the coaxial package, HHL package, H0 package, H1 package, H2 package, H3 package, and DIP package.
https://www.youtube.com/watch?v=35JE3dIAnNA