Compact dual-wavelength blue-green laser for airborne ocean detection lidar

Abstract

We have demonstrated a dual-wavelength blue-green laser for airborne ocean lidar based on an all-solid-state master oscillator power amplifier and nonlinear frequency conversion methods. A Q -switched pulsed laser with 10 mJ energy at 1064 nm was amplified to 108 mJ by a Nd:YAG amplifier side pumped by vertical-cavity surface-emitting laser modules. This fundamental laser was then frequency tripled to 355 nm wavelength by lithium triborate (LBO) crystals. With maximum pump energy of 43.5 mJ at 355 nm, 9.6 mJ of blue laser pulse at 486.1 nm was successfully obtained from an optical parametric oscillator unit using two beta-barium borate crystals. The energy of the residual 532 nm laser pulse was 10.6 mJ. Equipped with this laser system, an airborne blue-green lidar was developed, and ocean detection was carried out in the South China Sea, where an optical vertical profile at seawater depth of 94 m was obtained.

486 nm pulsed Nd:YLF laser with intracavity sum-frequency mixing

“…When 8.82 mJ total fundamental laser energy was applied, the cumulative spectrum was recorded during 2 min, which already contained the output wavelength stability. The central laser wavelength was measured to be 486.4 nm with the spectral bandwidth of 0.08 nm, much less than the typical spectral bandwidth of around 0.3 nm obtained by the OPO method [1,3], as shown in figure 3. According to formula (1), the laser wavelength λ 3 generated by sum-frequency can be given by…”

“…Compact solid-state pulsed lasers operating at 486 nm have been extensively applied in ocean detection lidar and underwater communication [1][2][3]. The blue laser in the region of 470-490 nm is well suitable for the open ocean applications due to its quite high transmission in deep seawater [4].…”

“…By now, optical parametric oscillator (OPO) is the most common way to generate high power blue laser pulse. In an OPO cavity with BBO crystals, pumped by 355 nm ultraviolet pulsed laser, 486 nm blue pulsed laser can be obtained [1][2][3]. However, the 355 nm pulsed laser was not emitted directly from the laser gain crystal, and was generated by frequencytripling of the fundamental laser at 1064 nm.…”

Hollow‐Core Fiber: Breaking the Nonlinearity Limits of Silica Fiber in Long‐Distance Green Laser Pulse Delivery

“…[26,47,48] Such single-mode outputs also potentially benefit long-distance underwater/space ranging due to their low beam divergence. [49,50]…”

Study on the effect of chlorophyll content in seawater on light transmission characteristics

“…For class 1 seawater and part of class 2 seawater that does not contain suspended mud, gravel, and quartz, the impurity components in seawater are phytoplankton of different concentrations, and the concentration of chlorophyll ranges from 0-12 mg/m 3 , so the light transmission characteristics of such seawater can only consider the influence of the concentration of chlorophyll. Blue-green lasers have been widely used in marine laser communication, above or underwater lidar, and 532 nm lasers have been widely used in target tracking, underwater target imaging, and chlorophyll fluorescence remote sensing [8]. In recent years, with the development of semiconductor lasers, researchers have carried out a series of works using blue-violet lasers in the qualitative and quantitative analysis of ship oil spills, CDOM, and chlorophyll.…”