microlasers

Microlasers are compact lasers in which the active gain region and the optical feedback mechanism are confined to micron-scale dimensions. They typically operate with resonators whose linear dimensions are on the order of a few micrometers or less, enabling low threshold powers and potential integration with microelectronic or photonic circuits.

Common microlasers use microcavities such as microdisks, microrings, microspheres, nanowires, or photonic crystal cavities to provide feedback by total internal reflection or photonic bandgap effects. Lasing occurs when optical gain compensates losses within the resonator. High quality factors and small mode volumes can reduce the threshold and enable single-mode operation; some devices exhibit large beta factors that further lower the apparent threshold.

Fabrication often involves epitaxial growth of semiconductor gain media followed by lithography and etching to define microcavities, or bottom-up synthesis of nanowires and quantum-dot based cavities. Materials include III-V semiconductors (GaAs, InP) for near-infrared to telecom wavelengths, GaN or ZnO for ultraviolet, and organic or polymer gain media for flexible, low-cost devices.

Applications span integrated photonics, on-chip optical interconnects, sensing, and biotechnology. Microlasers provide compact light sources that can be electrically pumped or optically pumped, enabling on-chip communication and portable sensing platforms.

Challenges include controlling emission directionality and spectral stability, achieving efficient electrical injection, thermal management, and reliable coupling of emitted light to fibers or waveguides. Ongoing research seeks higher efficiency, room-temperature operation, and scalable fabrication.