Self-frequency-doubling of ultrafast laser inscribed neodymium doped yttrium aluminum borate waveguides

Abstract

Buried channel optical waveguides, supporting orthogonal polarizations, have been fabricated in a neodymium doped yttrium aluminum borate nonlinear laser crystal by ultrafast laser inscription following the so-called "double line" approach. Confocal fluorescence and second harmonic imaging experiments have revealed that the original fluorescence and nonlinear properties have been not deteriorated by the waveguide inscription procedure. Preliminary laser experiments have shown the ability of the fabricated structures for green laser light generation under 808 nm optical pumping by self-frequency-doubling of the 1.06 m laser line of neodymium ions. © 2011 American Institute of Physics. ͓doi:10.1063/1.3584852͔Among the multifunctional optical systems currently proposed as building-blocks of integrated devices, selffrequency-converted ͑SFC͒ laser crystals are one of the most widely studied. SFC systems are constituted by a nonlinear crystal which is optically activated by laser ions ͑usually rare earth ions such as Nd 3+ or Yb 3+ ͒. 1 Under laser operation the nonlinear properties of the host matrix activate frequencymixing processes between the different intracavity laser radiations that propagate along the gain medium ͑pump and laser͒. These intracavity nonlinear processes lead to the generation of new laser frequencies without the requirement of additional intracavity optical components, i.e., allowing for highly compact multiwavelength laser sources. 1 Among the different SFC crystals reported up to now, neodymium doped yttrium aluminum borate ͑hereafter Nd:YAB͒ is, without doubts, a paradigm. 2 It combines the good thermal, mechanical, and nonlinear properties of the YAB host with the outstanding fluorescence properties of Nd ions. 3,4 Based on this unique combination, multifrequency laser light oscillation in the three fundamental colors ͑red, green, and blue͒ has been demonstrated from a unique Nd:YAB element operating at 1.3 m. 5 In its simplest version, involving only the second harmonic ͑SH͒ of the 1064 nm laser line of Nd 3+ ions, pumpto-green optical conversion efficiencies as high as 25% have been reported. 6 Further incorporation of Nd:YAB SFC lasers in miniaturized optical devices requires the controlled fabrication of optical waveguides ͑WGs͒ in the bulk material. Up to now, WGs in Nd:YAB crystals have been only reported by light ion implantation, without demonstrating any selffrequency-doubling ͑SFD͒ laser ability. 7 In order to achieve this goal the fabricated structures should satisfy following three main requirements: ͑i͒ the fabrication procedure should preserve the original fluorescence and nonlinear properties of the Nd:YAB system, ͑ii͒ the fabricated WGs should support both TE and TM modes so that birefringence-based phase matching ͑PM, requiring orthogonal polarizations for fundamental and second harmonic waves͒ will be possible, and ͑iii͒ light confinement should be achieved in a large spectral range so that spatial confinement of both fundamental and second order radiation would be achieve...

Ultrafast lasers—reliable tools for advanced materials processing

“…95 Optical waveguides can be easily inscribed in transparent materials such as glass, crystalline materials and polymers by inducing permanent refractive index changes in the focal volumes of tightly focused femtosecond laser pulses. 44 The waveguides are typically written in transparent materials using a transverse writing scheme, where the sample is translated perpendicular to the beam propagation direction.…”

Multi-wavelength emission through self-induced second-order wave-mixing processes from a Nd3+ doped crystalline powder random laser

“…4), which correspond to the second-harmonic and the Stokes stimulated Raman scattering, respectively. More recently self-frequency doubling was exploited in waveguide lasers5 and high efficient operation of CW upconversion laser6. Besides this fascinating physical phenomenon, it is interesting from the applied point of view to exploit processes of frequency conversion inside a unique medium.…”

Near-infrared lasers and self-frequency-doubling in Nd:YCOB cladding waveguides

“…The highest green laser powers generated from WG2 and WG3 are 64 μW and 80 μW, when the absorbed pumping powers at 806 nm are 62.7 mW and 69.5 mW, respectively. Compared with the previous works on the SFD waveguide laser [14,[19][20][21], the green laser powers achieved from these cladding structures are significantly larger. As a matter of fact, approximately 30 μW green laser radiation was obtained from a swift Ar 8+ ion irradiated Nd:YCOB planner waveguide and double-line channel waveguides in Nd:YAB crystal [14,19].…”

“…Compared with the previous works on the SFD waveguide laser [14,[19][20][21], the green laser powers achieved from these cladding structures are significantly larger. As a matter of fact, approximately 30 μW green laser radiation was obtained from a swift Ar 8+ ion irradiated Nd:YCOB planner waveguide and double-line channel waveguides in Nd:YAB crystal [14,19]. Although not having as high power levels as those obtained from Nd:YCOB bulk crystal [4,7], the cladding waveguide laser SFD systems are more advantageous for low pumping power due to the highly compact oscillation, which leads to high intra-cavity intensity.…”