Waveguides In Nd Research Articles

Optical ridge waveguides in Nd3+‐doped fluorophosphate glasses fabricated by carbon ion implantation and femtosecond laser ablation

AbstractIn this work, the ridge waveguide was formed by the femtosecond laser ablation with a central wavelength of 0.808 μm and a speed of 50 μm/s on the planar Nd3+‐doped fluorophosphate glass waveguide that was fabricated by the C3+ ion implantation with an energy of 6.0 MeV and a fluence of 1.0×1012 C3+s/mm2. The mechanism of the ion‐implanted waveguide was discussed by the Stopping and Range of Ions in Matter 2013. The cross‐section morphology of the ridge waveguide was captured by an optical microscope. Its mode characteristics were analyzed by the end‐face coupling method. The ridge Nd3+‐doped fluorophosphate glass waveguides have potential as fundamental structures for many optoelectronic devices including waveguide amplifiers and lasers.

Femtosecond-laser-written helical cladding waveguides: 3D fabrication and mode modulation

We report on the design and fabrication of helical cladding waveguides in Nd:YAG crystal by using femtosecond laser direct writing. These circular cladding shapes waveguides are characterized through the end-face coupling at 1064 nm, possessing good guiding properties and low bending losses. The helical waveguide structure has a minimum bending loss of 0.55 dB/cm. The mode modulation has been achieved by altering helix geometry parameters. The polarization dependence of these waveguides is kept at a relatively low level. In addition, an S-bend waveguide has been fabricated, indicating that helical structure increases bending loss by enhancing the interaction between the light and boundaries. This study paves the way for the fabrication of photonic circuits with complex 3D structures in crystals.

Bending 90° Waveguides in Nd:YAG Crystal Fabricated by a Combination of Femtosecond Laser Inscription and Precise Diamond Blade Dicing

In this paper, a low-loss 90°-bending design in femtosecond laser-induced double-line waveguides is theoretically proposed and experimentally demonstrated. The bending is realized based on the total internal reflection of a corner mirror (made by precise diamond blade dicing) located at the intersection of a pair of waveguides perpendicular to each other. The waveguide bending performance was birefringence free, with the insertion loss of each bending below 0.8 dB. This method provides great flexibility and has great potential for the design of integrated photonics based on femtosecond laser-inscribed crystalline materials.

Tapered depressed-cladding waveguide lasers modulated by Ag nanoparticles embedded in SiO2

We report on fabrication of tapered circular depressed-cladding waveguides in Nd:YAG crystal by femtosecond laser direct writing (FsLDW). Based on the fabricated waveguides, for the first time to the best of our knowledge, efficient Q-switched mode-locked (QML) lasers are realized by employing silver nanoparticles (NPs) embedded in fused silica as saturable absorber (SA) element. Laser pulses as short as 25 ps with a repetition rate of 7.7 GHz are generated at a wavelength of 1064 nm. We systematically explore the influence of incident-output facet and the reduction factors on guiding properties and laser performance by conducting a comparative study of different tapers, and it has been found that the waveguides with tapered structures can suppress multi-mode guiding while ensure fundamental-mode output for waveguide lasers. Our work paves a new way toward developing three-dimensional (3D) waveguide for applications in on-chip ultrafast laser sources.

Femtosecond laser direct writing of depressed cladding waveguides in Nd:YAG with "ear-like" structures: fabrication and laser generation.

Low-loss depressed cladding waveguide architecture is highly attractive for improving the laser performance of waveguide lasers. We report on the design and fabrication of the "ear-like" waveguide structures formed by a set of parallel tracks in neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal via femtosecond laser writing. The obtained "ear-like" waveguides are with more symmetric mode profiles and lower losses by systematically comparing the guiding properties of two kinds of normal cladding waveguide. Efficient waveguide lasers are realized based on the designed structure in both continuous wave and pulsed regimes. Combined the high-gain from cladding waveguide and special "ear-like" structure, a passively fundamentally Q-switched laser with the narrow pulse width and the high repetition rate has been obtained by using tin diselenide (SnSe2) as saturable absorber.

Cladding waveguide lasers in femtosecond laser written Nd:KGW waveguides

Buried cladding waveguides in Nd:KGW crystals were fabricated by femtosecond laser writing at a repetition rate of 500 kHz. Excellent waveguiding performance with low insertion loss of 1.8 dB at 1.06 μm wavelength was obtained. The waveguide is also characterized by Raman spectroscopy. Under optical pump of 806 nm light, continuous-wave waveguide lasers at 1067 nm have been achieved at room temperature. Fundamental- and high-order-mode guiding and lasing were realized by varying the waveguide diameter. A 40-μm diameter waveguide generates the maximum output power 198.5 mW with a slope efficiency of 39.4%.

Femtosecond-Laser-Written S-Curved Waveguide in Nd:YAP Crystal: Fabrication and Multi-Gigahertz Lasing

We report on the design and fabrication of straight and S-curved waveguides in neodymium-doped yttrium aluminate (Nd:YAP) crystal by using direct femtosecond laser writing. These S-curved channel waveguides are based on the hexagonal optical-lattice-like and depressed cladding geometry. For each type waveguide, S-curves with three lateral offsets of 50 μm, 100 μm, and 150 μm are implemented. These waveguides are with good guiding properties and low bending losses. With S-curved waveguide as laser cavity, dual-wavelength, 31.6 GHz waveguide laser operating at 1064 nm and 1079 nm have been demonstrated based on MoS2 as a saturable absorber. This work paves the way to develop new on-chip ultrafast laser sources based on femtosecond laser inscribed S-curved waveguides.

Fabrication of Tapered Circular Depressed-Cladding Waveguides in Nd:YAG Crystal by Femtosecond-Laser Direct Inscription.

Crystalline materials are excellent substrates for the integration of compact photonic devices benefiting from the unique optical properties of these materials. The technique of direct inscription with femtosecond lasers, as an advantage over other techniques, has opened the door to the fabrication of true three-dimensional (3D) photonic devices in almost any transparent substrate. Depressed-cladding waveguides have been demonstrated to be an excellent and versatile platform for the integration of 3D photonic circuits in crystals. Here, we present the technique that we have developed to inscribe tapered depressed-cladding waveguides with a circular section for the control of the modal behavior. As a proof of concept, we have applied the technique to fabricate structures in Nd:YAG crystal that efficiently change the modal behavior from highly multimodal to monomodal, in the visible and near infrared, with reduction factors in the waveguide radius of up to 4:1. Our results are interesting for different devices such as waveguide lasers, frequency converters or connectors between external devices with different core sizes.

Refractive index enhanced well-type waveguide in Nd:YGG crystal fabricated by swift Kr8+-ion irradiation

In this work, we introduced a Nd:YGG single mode planar waveguide fabricated by swift heavy ion irradiation. The initial Kr8+ ions beam energy was 2.1 GeV, after passing through the Al foil the beam energy came to 30 MeV. The implantation fluence was 2×1012 ions/cm2. A well region with the refractive index increment in near the surface was obtained after ion irradiation. This index increment was attributed to the ion-induced electronic damage. The characterization of the optical planar waveguide in Nd:YGG crystal was tested by prism coupling and end face coupling method. The micro-luminescence and Raman properties of our ion-irradiation Nd:YGG crystal were investigated. This work has reference value for integrated optical devices on Nd:YGG crystal.

Specklegram temperature sensor based on femtosecond laser inscribed depressed cladding waveguides in Nd:YAG crystal

In this paper, waveguide specklegram sensor (WSS) in Nd:YAG crystal for temperature sensing based on the average intensity variation of speckle patterns has been demonstrated. The temperature sensing resolution of the WSS has been identified as high as 0.05 °C. WSS in diverse-guiding geometries with different dynamic range for the temperature sensing has been obtained. In addition, the WSS own a much more sensitive performance to temperature variation when the laser with shorter wavelength and higher power is utilized. Benefit from the compact structure, WSS can be integrated in to a lab-on-chip system offering real-time monitoring of temperature.

The formation and characterization of optical waveguide in Nd:YLF crystal by 4.5-MeV Si ion implantation

The planar waveguides have been fabricated in Nd:YLF crystals by Si implantation. The guiding properties of Si-implanted waveguide are evaluated by the prism-coupling technique and reflectivity calculation method (RCM), exhibiting good confinement and monomode behavior at 632.8 nm. The investigation of the photoluminescence (PL) measurement demonstrates that the luminescence characteristics of the Nd3+ ions are not significantly altered by the Si ions irradiation process, whereas the up-conversion (UC) luminescence intensity can be effectively improved. Based on the pump-power-dependent fluorescence, the possible emission mechanism in Nd:YLF is proposed.

Annular waveguide lasers at 1064 nm in Nd:YAG crystal produced by femtosecond laser inscription.

We report on the fabrication of annular cladding waveguides in Nd:YAG laser crystal by using femtosecond laser inscription. The circular cross sections of the optical waveguides were in dual-cladding and tri-cladding shapes with different diameters. Under the optical pump at 808nm, the generated continuous-wave lasers at 1064nm have been realized in the annular cladding waveguides. For dual-cladding and tri-cladding waveguides, the slope efficiencies of the waveguide lasers were calculated to be 21.3% and 20%, and the maximum output powers measured were 82mW and 84mW, respectively. In addition, the annular modal profiles were obtained for these cladding waveguides.

Optical and structural properties of Nd:MgO:LiNbO3 crystal irradiated by 2.8-MeV He ions

We report the optical and structural properties of helium-implanted optical waveguides in Nd:MgO:LiNbO3 laser crystals. The prism-coupling method is used to investigate the dark-mode properties at the wavelength of 632.8 nm. The spontaneous generation of ultraviolet, blue, red, and near-infrared fluorescence emissions is demonstrated under excitation with an 808-nm laser diode. The effects of ion irradiation on the structural properties are characterized using the high-resolution X-ray diffraction technique. The results show that the initial luminescence properties of Nd:MgO:LiNbO3 crystals are slightly modified by irradiation with 2.8 MeV He ions at fluences of 1.5 × 1016 ions/cm2 at room temperature.

Optical waveguide in Nd:Bi12SiO20 crystal produced by multi-energy C ion implantation**Project supported by the National Natural Science Foundation of China (Grant Nos. 11404194 and 11274188), the Promotive Research Fund for Excellent Young and Middle-aged Scientisits of Shandong Province, China (Grant No. BS2015SF003), the China Postdoctoral Science Foundation (Grant Nos. 2015M582053 and 2016T90609), the Qingdao Municipal Postdoctoral Application Research Project, China

We report the fabrication of a planar waveguide in the Nd:Bi12SiO20 crystal by multi-energy C ions at room temperature. The waveguide is annealed at 200 °C, 260 °C, and 300 °C in succession each for 30 min in an open oven. The effective refractive index profiles at transverse electric (TE) polarization are stable after the annealing treatments. Damage distribution for multi-energy C ion implanted in Nd:Bi12SiO20 crystal is calculated by SRIM 2010. The Raman and fluorescence spectra of the Nd:Bi12SiO20 crystal are collected by an excitation beam at 633 nm and 473 nm, respectively. The results indicate the stabilization of the optical waveguide in Nd:Bi12SiO20 crystal.

Femtosecond laser inscription waveguides in Nd:GdVO4crystal

Channel waveguides in Nd:GdVO4 crystals were fabricated by using low-repetition-rate (1 kHz) femtosecond laser inscription. The influences of pulse energy and scanning velocity were investigated. Guiding occurs in the surroundings of the focal spot. Single-line, double-line, and double-layer waveguides were realized. The near-field mode images, refractive-index profile reconstruction, and mode analysis of waveguides are presented. The double-line waveguides show strong guidance at 632.8 nm with a loss of about 0.5 dB/mm and an index increase of 3×10−4. The mode profile asymmetry of single-line waveguide has been improved by using multipass scanning.

Femtosecond Laser Inscribed Y-Branch Waveguide in Nd:YAG Crystal: Fabrication and Continuous-Wave Lasing

Rectangular Y-branch cladding waveguides have been fabricated in Nd:YAG crystal by femtosecond laser inscription. Such novel configurations are fabricated with depth of 50 μm, supporting multimode guidance in both TM and TE polarizations. Continuous wave laser oscillations at wavelength of 1.06 μm have been achieved under the optical pump at 808 nm. The maximum output power is 0.2 W with a slope efficiency of 20% in the device with splitting angle of 0.5°.

Optical ridge waveguides in Nd:LGS crystal produced by combination of swift C5+ ion irradiation and precise diamond blade dicing

We report on the fabrication of optical ridge waveguides in Nd:LGS crystal by using combination of swift C5+ ion irradiation and precise diamond blade dicing. The ridge structures support guidance both at 632.8nm and 1064nm wavelength along the TE and TM polarizations. The lowest propagation losses of the ridge waveguide for the TM mode are ~1.6dB/cm at 632.8nm and ~1.2dB/cm at 1064nm, respectively. The investigation of micro-fluorescence spectra and micro-Raman spectra indicates that the Nd3+ luminescence features have been well preserved and the microstructure of the waveguide region has no significant change after C5+ ion irradiation.

Stress-induced waveguides in Nd:YAG by simultaneous double-beam irradiation with femtosecond pulses

We report on the fabrication of stress-induced waveguides in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) by simultaneous double-beam irradiation with femtosecond laser pulses. An interferometer was used to generate two femtosecond laser beams that, focused with certain lateral separation inside the crystal, produced two parallel damage tracks with a single scan. The propagation of the mechanical waves simultaneously created in both focal spots produced a highly symmetrical stress field that is clearly revealed in micro-luminescence maps. The optical properties of the double-beam waveguides are studied and compared to those of single-beam irradiation, showing relevant differences. The creation of more symmetric stress patterns and a slight reduction of propagation losses are explained in terms of the fact that simultaneous inscription allows for a drastic reduction in the magnitude of “incubation” effects related to the existence of pre-damaged states.

Fabrication and characterization of carbon/oxygen-implanted waveguides in Nd 3 + -doped phosphate glasses

Optical planar waveguides in Nd-3-Hdoped phosphate glasses are fabricated by a 6.0-MeV carbon ion implantation with a dose of 6.0 x 1014 ions/cm2 and a 6.0-MeV oxygen ion implantation at a fluence of 6.0 x 1014 ions/cm(2), respectively. The guided modes and the corresponding effective refractive indices were measured by a modal 2010 prism coupler. The refractive index profiles of the waveguides were analyzed based on the stopping and range of ions in matter and the RCM reflectivity calculation method. The near-field light intensity distributions were measured and simulated by an end-face coupling method and a finite-difference beam propagation method, respectively. The comparison of optical properties between the carbon-implanted waveguide and the oxygen-implanted waveguide was carried out. The microluminescence and Raman spectroscopy investigations reveal that fluorescent properties of Nd3- ions and glass microstructure are well preserved in the waveguide region, which suggests that the carbon/oxygen-implanted waveguide is a good candidate for integrated photonic devices. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Passively Q-switched Nd:YVO4 waveguide laser using graphene as a saturable absorber

We report on passively Q-switched lasers in femtosecond laser written waveguide in Nd:YVO4 crystal. Using graphene as a saturable absorber, passively Q-switched waveguide laser operations are achieved along both TE and TM polarizations with single modal profiles. Furthermore, all-angle linear light pump was utilized to investigate the thorough information of the polarization effects of the laser, showing that the optimum polarization for laser generation is TE. The maximum average output power is estimated to be 129mW with 12.2% slope efficiency, corresponding to single-pulse energy of 8.1nJ, pulse duration of 25.0ns and repetition rate of 16.3MHz.