Fabrication and characterization of femtosecond laser written waveguides in chalcogenide glass

Hughes, Mark A.; Yang, Weijia; Hewak, Daniel W.

doi:10.1063/1.2718486

Cited by 103 publications

(39 citation statements)

References 20 publications

(21 reference statements)

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“…Highly asymmetric features are seen due to a combination of spherical aberration and strong nonlinear material interaction (Fig. 1A), which is consistent with the work of Hughes et al [6]. One guided mode was observed at 1560 nm in the "head" of the modified zone (Fig.…”

supporting

confidence: 81%

“…However, this large nonlinearity has strong impacts on laser pulse propagation, producing such phenomena as self-focusing. These effects lead to an elongation of the laser modified region within the substrate, yielding multiple guiding regions as reported in early work [6]. More recently, multiple laser passes have yielded more symmetrical features in CHG glasses, producing single-mode guiding in the mid-IR spectral range (3-11 μm) [7].…”

mentioning

confidence: 81%

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Ultrafast laser fabrication of low-loss waveguides in chalcogenide glass with 065 dB/cm loss

et al. 2012

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This Letter reports on the fabrication of low-loss waveguides in gallium-lanthanum-sulfide chalcogenide glasses using an ultrafast laser. Spatial beam shaping and temporal pulse width tuning were used to optimize the guided mode profiles and optical loss of laser-written waveguides. Highly symmetric single-mode waveguides guiding at 1560 nm with a loss of 0.65 dB∕cm were fabricated using 1.5 ps laser pulses. This Letter suggests a pathway to produce high quality optical waveguides in substrates with strong nonlinearity using the ultrafast laser direct writing technique. © 2012 Optical Society of America OCIS codes: 350.3390, 130.2755, 160.4330, 130.4310. Over the last decade, the ultrafast laser has emerged as a powerful tool to shape three-dimensional (3D) photonic circuits in transparent dielectric materials [1]. Research efforts invested since its first demonstration have extended this 3D fabrication approach to a wide array of optical substrates, including those with optical gain [2] and strong optical nonlinearities [3]. One of the unique traits of this fabrication approach is its ability to produce photonic circuits in bulk optical substrates with proven optical quality. It therefore bypasses all challenges associated with multi-step thin film based material synthesis and fabrication techniques. An important aspect of the ultrafast laser device fabrication process is to optimize the processing parameters to improve the optical qualities of these 3D waveguides. This was normally achieved through the proper choice and fine-tuning of several factors including repetition rate, wavelength, writing speed, and pulse energy of the writing laser. In many situations, however, adjustment of these parameters is not sufficient to produce optical devices with satisfactory performance. An example that highlights this challenge is the ultrafast laser processing of chalcogenide (CHG) glasses. With a high nonlinearity and wide IR transmission window, CHG glasses have recently attracted much attention for potential applications in all-optical switching [4] and mid-IR photonics [5]. However, this large nonlinearity has strong impacts on laser pulse propagation, producing such phenomena as self-focusing. These effects lead to an elongation of the laser modified region within the substrate, yielding multiple guiding regions as reported in early work [6]. More recently, multiple laser passes have yielded more symmetrical features in CHG glasses, producing single-mode guiding in the mid-IR spectral range (3-11 μm) [7]. However, the fabrication of highly symmetric single-mode waveguides at shorter wavelengths (e.g., 1560 nm) remains a significant challenge. The effects of beam distortion due to nonlinear material interaction are difficult to mitigate through the optimization of laser writing parameters alone. Additionally, fabrication of these features is made more difficult due to the high refractive index of CHG glass, which induces spherical aberrations and distorts the focus at depths larger than a few tens of micrometers....

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confidence: 81%

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confidence: 81%

Ultrafast laser fabrication of low-loss waveguides in chalcogenide glass with 065 dB/cm loss

et al. 2012

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“…Since the index change measurement represents the index change induced by all of the waveguide structure along the z axis it remains a possibility that region 1 has undergone a nega- tive index change. In previous work we reported that region 1 has a lower reflectivity than the surrounding glass [20], indicating it has undergone a negative index change. Region 2 had a higher reflectivity and guided light, indicating it had undergone a positive index change.…”

Section: B Refractive Index Change Profilementioning

confidence: 99%

“…In previous work, we reported initial results on fs laser written waveguides in GLS glass [20]. In this work, we report details on the fabrication and characterization of these waveguides and give a more complete discussion of the waveguide formation mechanism.…”

Section: Introductionmentioning

confidence: 99%

Spectral broadening in femtosecond laser written waveguides in chalcogenide glass

2009

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Nonlinear spectral broadening to 200 nm, from an initial width of 50 nm, has been demonstrated in gallium lanthanum sulphide glass waveguides from 1540 nm, 200 fs pulses at 30 nJ/pulse. A formation mechanism is presented for these femtosecond laser written waveguides, based on optical characterization and comparisons to previous work. Two different types of waveguide are identified. One has a characteristic long narrow structure and is formed through filamentation caused by self-focusing. The other has a characteristic "teardrop" structure, which is formed by a type IIA photosensitivity mechanism and cumulative heating of glass around a central laser-exposed region.

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“…The high refractive index of these materials induces spherical aberrations at the focus of the writing beam, which are further compounded by nonlinear effects brought about by high-intensity laser pulses. These interactions often lead to self-focusing and filamentation, producing highly asymmetrical waveguides with an elongated cross section and multiple guiding regions [15]. Mitigation of these effects is essential for fabricating high-quality waveguides in ChG glasses.…”

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confidence: 99%

Ultrafast laser fabrication of Bragg waveguides in chalcogenide glass

McMillen

Huang

et al. 2014

Opt. Lett.

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Bragg waveguides are fundamental components in photonic integrated circuits and are particularly interesting for mid-IR applications in high index, highly nonlinear materials. In this work, we present Bragg waveguides fabricated in bulk chalcogenide glass using an ultrafast laser. Waveguides with near circularly symmetric cross sections and low propagation loss are obtained through spatial and temporal beam shaping. Using a single-pass technique, the waveguide and Bragg structure are formed at the same time. First through sixth order gratings with strengths of up to 25 dB are realized, and performance is evaluated based on the modulation duty cycle of the writing beam. Chalcogenide (ChG) glasses are known for their excellent mid-IR transparency and large nonlinear refractive indices of up to 1000 times that of fused silica [1,2]. These unique traits make them attractive in a wide range of applications. In particular, ChG glasses are suitable substrate materials for fabricating photonic integrated circuits (PICs), due to inherently large χ 3 nonlinearities with ultrafast response times and low two-photon absorption at telecom wavelengths. These properties become especially important in applications such as high-data-rate signal processing [3][4][5]. In such PIC devices, Bragg waveguides are often employed as basic building blocks, enabling operations such as 2R regeneration [6,7], and all-optical switching [8]. Fabrication of these structures generally relies on thin film deposition and various photolithography schemes. However, thin-film processes incur restrictions when building multilayer structures for complex optical interconnects by limiting devices to a planar geometry. Ultrafast laser writing offers great design flexibility with its capability for making three-dimensional structures [9,10] and is a proven technique to form high-quality waveguides in bulk optical substrates. Extensions of this technology have also been applied to the fabrication of Bragg waveguides in fused silica using several approaches, such as the point-by-point technique [11][12][13], and the multiscan technique [14]. Applying these methods to ChG glasses, however, presents a unique design challenge. The high refractive index of these materials induces spherical aberrations at the focus of the writing beam, which are further compounded by nonlinear effects brought about by high-intensity laser pulses. These interactions often lead to self-focusing and filamentation, producing highly asymmetrical waveguides with an elongated cross section and multiple guiding regions [15]. Mitigation of these effects is essential for fabricating high-quality waveguides in ChG glasses.Recently, it has been demonstrated that temporal [16] and spatial beam shaping [17] may be used to control the size and shape of the cross section of a laser-written waveguide. These techniques, combined with adjustment of other processing parameters such as writing speed, pulse energy, and repetition rate, have produced nearly symmetric waveguides with propagation losses ...

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Fabrication and characterization of femtosecond laser written waveguides in chalcogenide glass

Cited by 103 publications

References 20 publications

Ultrafast laser fabrication of low-loss waveguides in chalcogenide glass with 065 dB/cm loss

Ultrafast laser fabrication of low-loss waveguides in chalcogenide glass with 065 dB/cm loss

Spectral broadening in femtosecond laser written waveguides in chalcogenide glass

Ultrafast laser fabrication of Bragg waveguides in chalcogenide glass

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