Scheme
These lasers consist of a lateral single-moded RW section with integrated Bragg grating and a section with a flared contact where the laser light is amplified. Depending on the position of the grating within the cavity, different types depicted below can be distinguished. The active pumped areas are marked gray.
In a DBR tapered laser (a) a rear unpumped passive grating section is forming a back mirror. Hence, its operating principle is similar to that of a tapered laser except for the wavelength-selective rear reflectivity.
If an additionally unpumped passive grating is integrated at the other side of the RW section, this part of the device operates as an independent DBR laser (b). Therefore, in this so-called monolithically integrated MOPA (master-oscillator power-amplifier) the light emitted by the DBR laser is directly coupled into the tapered section where it is amplified. For a stable operation an extremely good anti-reflection coating of the facet of the tapered section is essential.
In another type, the RW section can be designed as an independently working DFB laser with a pumped active grating (c).
Applications
- Free space communication
- Non-linear frequency conversion
- Medical applications
- Pump source of fiber lasers and amplifiers
Chip technology
- Semiconductor layer structures grown with MOVPE
- Combination of RW and BA laser technology
- Two-step epitaxy: After the first growth implementation of the Bragg grating in the waveguide utilizing holographic lithography and wet-chemical etching, subsequent overgrowth of the structured surface
- Single-step epitaxy: Implementation of the Bragg grating from the surface of the complete epitaxial layer structure utilizing i-line wafer stepper or e-beam lithography and dry etching
