What is a DBR laser diode

A DBR (Distributed Bragg Reflector) laser diode is a single-frequency semiconductor laser with a wavelength-selective Bragg grating providing stable, narrow-linewidth output.

Structure and Operation

A DB

R laser diode consists of two main sections: a gain section where the laser light is generated, and a DBR section containing a Bragg grating that acts as a wavelength-selective reflector. The grating provides feedback only for a specific longitudinal mode, ensuring single-frequency operation. The resonator is typically formed by the DBR mirror on one end and a low-reflectivity cleaved facet on the other, with the laser emitting from the exit facet opposite the DBR.

The device may also include a phase section to enable mode-hop-free tuning. Key CharacteristicsSingle-frequency output: DBR lasers operate on a single spatial and longitudinal mode, producing a diffraction-limited beam. Narrow linewidth: Typical linewidths are a few megahertz, making them suitable for high-precision applications.

Tuning: Wavelength tuning is possible by adjusting the current or temperature of the gain or DBR section. The tuning range is usually a few nanometers, with temperature coefficients around 0. 07 nm/K and current coefficients about 0.

003 nm/mA. More advanced designs, like SG-DBR lasers, can achieve wider tuning ranges using Vernier effects. Output power: Standard DBR diodes provide moderate power, but MOPA (Master Oscillator Power Amplifier) configurations can exceed 100 mW, and broad-area diodes can reach several watts.

Comparison with Other Single-Frequency LasersDBR lasers are similar to DFB (Distributed Feedback) lasers in providing single-frequency output, but the grating in a DBR is external to the gain region, whereas in DFB lasers it is embedded within the active region.

DB

R lasers may exhibit periodic mode hops during tuning, unlike DFB lasers which can maintain mode-hop-free operation over their tuning range. Compared to external cavity lasers, DBR diodes are more compact but have slightly broader linewidths. ApplicationsDBR laser diodes are widely used in: Spectroscopy and high-resolution sensingLaser cooling and atomic physics experimentsGas detection and environmental monitoringTunable coherent sources for telecommunications and terahertz generation Their combination of narrow linewidth, tunability, and stable single-mode operation makes them ideal for precision optical systems.