Multiphoton microscopy with a short pulse laser has emerged as a powerful biomedical tool for cancer and Alzheimer's disease research and diagnosis. With advances in tunability, cost-efficiency, and compactness, semiconductor laser diodes have shown promising potential as wavelength-controlled pulsed light sources for these applications. Gain switching is a key method for short-pulse generation in semiconductor lasers, and femtosecond gain-switched pulses have already been demonstrated.

Precise and fast tunability or control in wavelength is attracting recent scientific, technological, and practical interests, and is achieved by distributed-feedback structures or by external-cavity-laser structures using silicon-photonics double-micro-ring-resonators. Each approach has its pros and cons, and appropriate methods must be selected to develop their most advantages based on application needs.

In this proposed research, with the collaboration with Akiyama lab in LASOR, we aim to study the physical mechanisms and limiting factors of several laser-pulse-control techniques, explore their fundamental limitations, and provide technical references for future applications.