Optical efficiency and gain dynamics of modelocked semiconductor disk lasers.

Area of Science:

• Optoelectronics
• Laser Physics
• Semiconductor Devices

Background:

• Semiconductor disk lasers (SDLs) offer versatile, high-repetition-rate, short-pulse generation.
• Vertical external-cavity surface-emitting lasers (VECSELs) and MIXSELs are key SDL architectures.
• Achieving ultrashort pulses in SDLs is crucial for advanced applications.

Purpose of the Study:

• To demonstrate record-short pulse durations from a gigahertz MIXSEL.
• To investigate the gain saturation behavior in SDLs at ultrashort pulse durations.
• To develop a quantum well model explaining modelocking performance limitations.

Main Methods:

• Experimental generation of 184 fs pulses from a 1048 nm MIXSEL.
• Experimental observation of reduced macroscopic gain saturation fluence with shorter pulses.
• Development of a quantum well model based on rate equations.

Main Results:

• Record-short 184 fs pulses achieved from a gigahertz MIXSEL.
• Optical-to-optical pump efficiency was <1% with limited output power.
• Shorter pulses were found to significantly reduce macroscopic gain saturation fluence.
• Spectral hole burning and short carrier lifetimes were identified as key limitations.

Conclusions:

• A quantum well model quantitatively explains MIXSEL and VECSEL modelocking performance.
• Spectral hole burning is the primary cause for reduced gain at shorter pulse durations.
• Understanding these limitations will guide future ultrafast SDL designs.