Flexible GaN-based ultraviolet microdisk lasers on PET substrate.

Flexible optoelectronics is a technique for fabricating optoelectronic devices on a flexible substrate. Compared with conventional devices, flexible optoelectronic devices can be used in more complex working environments benefiting from the mechanical flexibility. Herein, for the first time to the best of our knowledge, a flexible GaN-based microdisk laser on a polyethylene terephthalate (PET) substrate in the ultraviolet A (UVA) range was demonstrated by using thin film transfer process based on laser lift-off (LLO). The lasing wavelength is 370.5 nm with a linewidth of 0.15 nm and a threshold power density of 200 kW/cm. Additionally, a distributed Bragg reflector (DBR) was deposited on the backside of the microdisk as the bottom mirror between GaN microdisk and PET substrate, which can provide better mode confinement inside the microdisk and increases the oscillation intensity. The lasing wavelength of the flexible laser shows a 2-nm redshift under different bending curvature of the substrate, which is promising for applications such as mechanical sensing.