Abstract
In this paper, diode pumped solid state (DPSS) lasers based on end-pumping series N d : Y V O 4 and N d : G d V O 4 crystals were studied. Dual-, tri-, and quad-wavelength emissions were achieved. In the dual-wavelength emission operation, an optical-to-optical efficiency (O-O) of 48.9% and the power instability was 0.4% were obtained. These are the most efficient and compact lasers operating in continuous wave mode reported to date with series crystals. Besides this, the effect of changing power ratio between the output laser powers on speckle reduction was investigated for the first time. In addition, tri and quad wavelength emissions were achieved with a reasonable efficiency simply by optimizing the cavity parameters.
Highlights
Many methods have been reported to achieve multi-wavelength emission such as: inserting optical selective elements (OSE) inside a cavity like etalon [7] or birefringent filter [8], by two inequivalent emitting centers coexisting inside the laser crystal [9], by angle tuning for a laser crystal [10], pumping two distinct crystals separately [11], and pumping two different crystals simultaneously [12]
The dual-wavelength emissions from two series crystals has been demonstrated using a variety of pairs of laser crystals including Nd : YVO4 /Nd : GdVO4 [14], Nd : YVO4 /Nd : KGW [15], Nd : YVO4 /Nd : LuVO4 [15], Nd : YAG/Nd : YLF, and Nd : YLF/Nd : YLF [3]
continuous wave (CW) mode compact lasers based on the end-pumping series Nd : YVO4 /Nd : GdVO4 crystals with high optical-to-optical efficiency (O-O) efficiency, high stability, and low speckle contrast ratio have been achieved
Summary
Development of laser sources based on end-pumping of series laser crystals with multiple (dual/tri/quad) emission wavelengths has attracted attention due to their potential applications such as THz generation [1], precise spectroscopy [2], imaging [3], biomedical instrumentation [4], lidar [5], and nonlinear scientific research of optical mixers [6]. For single gain medium based multi wavelength emissions their lasing wavelengths generally share the same upper energy level which makes their mode competition serious [13], the approach of end pumping series crystals [12] is considered to be a solution. It uses two separate gain mediums and each crystal has its unique wavelength. CW mode compact lasers based on the end-pumping series Nd : YVO4 /Nd : GdVO4 crystals with high O-O efficiency, high stability, and low speckle contrast ratio have been achieved
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