Tunable Picosecond Laser Pulses via the Contrast of Two Reverse Saturable Absorption Phases in a Waveguide Platform

Abstract

How to enhance the optical nonlinearity of saturable absorption materials is an important question to improve the functionality of various applications ranging from the high power laser to photonic computational devices. We demonstrate the saturable absorption (SA) of VO2 film attributed to the large difference of optical nonlinearities between the two states of the phase-transition materials (VO2). Such VO2 film demonstrated significantly improved performance with saturation intensity higher than other existing ultrathin saturable absorbers by 3 orders due to its unique nonlinear optical mechanisms in the ultrafast phase change process. Owing to this feature, a Q-switched pulsed laser was fabricated in a waveguide platform, which is the first time to achieve picosecond pulse duration and maintain high peak power. Furthermore, the emission of this VO2 waveguide laser can be flexibly switched between the continuous-wave (CW) and pulsed operation regimes by tuning the temperature of the VO2 film, which enables VO2-based miniature laser devices with unique and versatile functions.

Epitaxial VO2 Nanostructures: A Route to Large-Scale, Switchable Dielectric Metasurfaces

“…Artificially structured layers of materials have provided unprecedented optical functionalities − and facilitated miniaturization of conventional optical elements and devices like lenses − and polarimeters. , Although metasurfaces were originally based on noble metal plasmonics, an effort to increase their efficiency and bring new applications has led to utilization of new materials with reduced losses, especially dielectrics, − and materials with tunable optical properties . The latter class of materials is represented mainly by doped transparent conductive oxides (typically indium tin oxide), which can be readily controlled via electrostatic gating, and by phase transition materials (typically vanadium dioxide or germanium antimony telluride), − which can undergo a profound change of optical properties upon external stimuli (thermal, electrical, optical).…”

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials

“…Compared with the reported value of 14-nm pulse duration in the Q-switched erbium doped glass laser by utilizing the phase transition of a VO 2 film54, the Q-switched Nd:YVO 4 waveguide laser shows superior properties in the pulse duration based on VO 2 SAM in the insulating phase. It is worth mentioning that the 690-ps waveguide laser is realized at room temperature with the insulting phase of VO 2 , which has simpler and easily manipulation than the reported 700-ps waveguide laser generation during the transition from insulating to metallic phase of VO 2 45. Moreover, based on so-called Contrast Nonlinear Transmission, much shorter pulse duration could be implemented during the ultrafast phase transition process of VO 2 .…”

“…Moreover, in the aspect of maximum output power and slope efficiency, Q-switched waveguide laser with WS 2 SAM has the highest value among three nanomaterials based systems, which is still feasible to reach higher-power output by increasing the pump power. For VO 2 , the phase-change material, it may be transferred from pulsed regime to CW operation as the temperature of the system exceeds the VO 2 phase transition point due to the high-power laser induced heating effect45.…”

“…Tan et al . reported on tunable waveguide lasers on carbon ion implanted Nd:YAG waveguides with dynamic thermal controlling of the VO 2 mirror45. This mechanism is disparate with the SA of 2D materials based on photon-induced electronic excitation according to their band structures46.…”

Near-infrared saturable and reverse saturable absorption of ion beam synthesized VO2 nanocrystals

“…VO 2 based structures in general are envisioned for applications such as switchable optical elements [2,3] and the optical control of the phase of light [4]. More recent work incorporates VO 2 into hybrid structures involving, e.g., photonic crystals and waveguides [5,6]. Much less is known about the nonlinear optical properties of VO 2 .…”