Intra-pulse beam steering in a mid-infrared quantum cascade laser

Area of Science:

• Semiconductor Lasers
• Quantum Cascade Lasers
• Optoelectronics

Background:

• Quantum cascade lasers (QCLs) are semiconductor devices emitting in the mid-infrared to terahertz range.
• Beam steering in QCLs is crucial for applications like free-space optical communications and sensing.
• Understanding the dynamics of beam steering is essential for optimizing laser performance.

Purpose of the Study:

• To experimentally investigate and theoretically model the intra-pulse beam steering in an AlGaAs/GaAs quantum cascade laser.
• To analyze the influence of supply current on beam steering behavior and dynamics.
• To characterize the bistability and time-dependent changes in beam direction.

Main Methods:

• Intra-pulse measurements of beam steering were performed on an AlGaAs/GaAs quantum cascade laser.
• A two-mode theoretical model was employed to explain the experimental observations.
• The near-field radiation pattern was calculated using the effective index method.
• Numerical transposition to the far-field was achieved using Huygens' principle.

Main Results:

• A maximum beam deflection of [Formula: see text] was observed.
• For supply currents from 1.6 to 2.4 times the threshold, beam steering occurred unidirectionally.
• At higher currents, bidirectional and bistable beam steering was observed.
• The time period for beam direction change varied from approximately 40 ns to 20 ns with increasing current.

Conclusions:

• The study successfully characterized the beam steering dynamics in AlGaAs/GaAs quantum cascade lasers.
• A transition from unidirectional to bistable, alternating beam steering was identified at higher currents.
• The observed phenomena are explained by a two-mode theoretical model, providing insights into laser operation.