Inverted deposition and high-velocity spinning to develop buried planar chalcogenide glass waveguides for highly nonlinear integrated optics

Abstract

We report on buried planar waveguides in a highly nonlinear infrared transmitting chalcogenide glass, fabricated using a combination of inverted deposition of the molten glass phase and high-velocity spinning. Films of gallium lanthanum sulphide ͑Ga: La: S͒ glass were deposited onto an expansion coefficient matched Ga: La: S cladding substrate. These amorphous films, with an optimized composition designed to be resistant against crystallization, were observed to have an excellent interface quality and uniformity. The designed planar chip had a buried core, 6 m thick in the vertical direction, in single-mode operation at 1.064 m and a measured propagation loss of Ͻ0.2 dB cm −1 . Through this technique waveguides from Ga: La: S glass, a highly versatile optical semiconductor material, can potentially be used in nonlinear applications as well as provide passive and active integrated optic functionality into the infrared beyond 5 m. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1856686͔Highly nonlinear glass has the potential to address a wide range of technologies. However, the development of this glass technology in planar platforms currently lags a generation behind conventional glass ͑silica based͒ integrated optic research and development. A highly nonlinear IR and transmitting thin film/planar device can effectively operate in a variety of systems, e.g., optical switches and lasers, modulators, sensors, grating based devices, IR radiation conduits, antireflection coatings, data storage, and generation of supercontinuum. 1-4 Some examples of highly nonlinear materials include As-S, As-Se, Ge-S, Ge-Se-Te, and Ga-La-S. The increasing sophistication of the industries requiring optical thin films from unconventional materials calls for alternative fabrication methods to be matured, which is the subject of this letter. 5 In the highly nonlinear and IR transmitting family of materials, in particular the chalcogenide glasses ͑ChGs͒, the synthesis of thin films have been reported. 6-9 Chalcogenide glasses contain elements from group VI of the periodic table as glass-forming anions and are generally opaque in the visible, with the exception of some sulphide glasses, and exhibit transparency extending into the longer infrared wavelengths ͑5-15 m͒ as compared with conventional glasses. The high nonlinear refractive index, enhanced IR transmission coupled with reduced phonon energy, and the ability to exhibit localized photoinduced material changes ͑reversible or irreversible͒, suggest these glasses are indeed fascinating candidates for planar waveguide development. A noteworthy member of the ChG family is the gallium lanthanum sulphide ͑Ga: La: S͒ glass system, having an optical transparency between 0.5 and 10 m, a high glass transition temperature ͑T g ͒ of 580°C, high solubility of rare-earths, transition, and precious metals ͑e.g., silver and platinum͒ and controllable photosensitivity. 10 In addition, it has been reported that Ga: La: S optical glass has the highest optical nonlinearity as compared with other ...

Erbium-doped fluoride glass waveguides

“…Since the viscosity is more temperature dependent than the density, a temperature rise provokes thinner films. Although the rotation velocity is a squared term in the equation, the resulting poor film quality limits the use of high velocities [8]. With the parameters listed above, a film thickness of 30 μm was expected, which is consistent with the measured thickness (28 -32 μm).…”

Fabrication of heavy metal fluoride glass, optical planar waveguides by hot-spin casting

“…This is an inherent problem with the hot-spin casting technique and was also noted as a problem for HDSC [12,13].…”

“…6(a), Table 4). Table 3 Refractive indices measured across the visible spectrum by means of Abbe refractometry of the bulk-melted heavy metal fluoride glasses whose compositions are presented in Table 1 Wavelength ( [13] and ZBLALiYPb and HBLANY [14]. For the samples: HSC07, HSC09, HSC10, HSC11, HSC12 and HSC13 (all ZBLANPb-film-(core)-on-ZBLAN-substrate-(clad.…”

“…Two other processes, which are both simple, and similar, in concept, have been developed to produce optically-guiding thin films using infrared-transmitting glasses namely: Hot Dip Spin Coating (HDSC) [12,13] and hot-spin casting (HSC) [14,15]. Of all the reported techniques for making planar waveguides, these alone involve casting a thin film of the inorganic glass-forming liquid from above the liquidus, taking full advantage of cooling through the supercooled liquid state to aid shaping of the glass waveguide.…”

“…The Hot Dip Spin Coating technique described in [12,13] has been used to produce optical guiding films from both heavy metal fluoride [12] and chalcogenide [13] glasses, with a range of film thicknesses from a few tens of microns down to 2 lm. A double dipping process allowed spinning-on of an over cladding layer, with concurrent thinning of the initial core layer.…”