Arbitrary on-chip optical filter using complex waveguide Bragg gratings

Zhu, Tiecheng; Hu, Yiwen; Gatkine, Pradip; Veilleux, Sylvain; Bland-Hawthorn, Joss; Dagenais, M.

doi:10.1063/1.4943551

Cited by 60 publications

(31 citation statements)

References 21 publications

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“…A complex grating reflects a desired profile in wavelength, i.e., a filter can be constructed using this concept. Such a filter can be implemented in four ways: a) Individual SMFs [38], b) a multi-core bundle of single mode fibers [39,40], c) on-chip waveguide Bragg gratings [41], and d) 3D photonic Bragg gratings in a glass block using ULI [42]. So far, Bragg gratings on individual SMFs has been demonstrated on sky with ∼100 notches, with a rejection ratio of ∼1000 at a notch-width δλ ∼ 0.15 nm [30,43].…”

Section: Oh-emission Suppressionmentioning

confidence: 99%

“…Hence, fabrication process control is critical. These shortcomings are currently being alleviated significantly by improving the fabrication recipes and device modeling [41,45,46]. Considering the potential of combining the filtering and dispersion steps on the same chip (as shown in Figure 2), this line of ideas is worth exploring.…”

Section: Oh-emission Suppressionmentioning

confidence: 99%

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Astrophotonic Spectrographs

2019

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Astrophotonics is the application of photonic technologies to channel, manipulate, and disperse light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. Utilizing photonic advantage for astronomical spectroscopy is a promising approach to miniaturizing the next generation of spectrometers for large telescopes. It can be primarily attained by leveraging the two-dimensional nature of photonic structures on a chip or a set of fibers, thus reducing the size of spectroscopic instrumentation to a few centimeters and the weight to a few hundred grams. A wide variety of astrophotonic spectrometers is currently being developed, including arrayed waveguide gratings (AWGs), photonic echelle gratings (PEGs), and Fourier-transform spectrometer (FTS). These astrophotonic devices are flexible, cheaper to mass produce, easier to control, and much less susceptible to vibrations and flexure than conventional astronomical spectrographs. The applications of these spectrographs range from astronomy to biomedical analysis. This paper provides a brief review of this new class of astronomical spectrographs.Appl. Sci. 2019, xx, 5 2 of 18 of the telescope), creating new challenges for instrumentation [7]. At the same time, there is an explosion in the number of large astronomical surveys discovering a multitude of new transients, exoplanets, and galaxies. This necessitates development of new instruments for large telescopes that are compact and cost-effective while providing the flexibility to address the challenge of high-throughput characterization for these large surveys.Photonic technologies provide a promising platform for building next-generation instruments that are flexible (in terms of light manipulation), compact (volumes of a few tens of cubic centimetres) and lightweight (a few hundreds of grams), thanks to manipulation of guided light [8,9]. In addition, they are cost-effective, due to the advantages of mass-fabrication. Therefore, the astronomical community has pursued this direction very positively and built a wide variety of instruments from the near-ultraviolet (NUV) [10] to mid-infrared (MIR) wavebands [11]. As an example of the growth of astrophotonics, Figure 1 shows the number of citations of papers related to astrophotonic spectrographs. However, the current technical know-how is still far from complete or ideal, leaving many challenges that will likely be addressed in the near future.In this paper, we focus on the recent developments in the field of astrophotonic spectrographs. To paint a complete picture, in Sections 2 and 3, respectively, we briefly discuss the steps to channel the light from the telescope to the spectrograph and condition it. Photonic dispersion concepts, and their implementation and challenges are described in Section 4. In Section 5, we discuss new developments in calibration and detection that are particularly of interest to astrophotonic spectrographs. Lastly, in Section 6, we summarize and discuss the impact of photonic spectrogr...

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Section: Oh-emission Suppressionmentioning

confidence: 99%

Section: Oh-emission Suppressionmentioning

confidence: 99%

Astrophotonic Spectrographs

2019

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“…There have also been successful preliminary tests of using modified commercial AWGs for astronomical spectroscopy [16,17]. AWGs, along with other advances in the field of astrophotonics, such as photonic lanterns [18][19][20] to convert multimode fibers to single mode fibers, Bragg gratings (in fibers [21][22][23][24] as well as on chips [25]) to suppress the unwanted atmospheric OH-emission background (in the NIR), and high-efficiency fiber bundles for directly carrying the light from the telescope focal plane [26], offer a complete high-efficiency miniaturized solution for astronomical spectroscopy in the NIR. This solution has potential applications for future ground-, balloon-and space-based telescopes.…”

Section: Arrayed Waveguide Gratingsmentioning

confidence: 99%

Arrayed waveguide grating spectrometers for astronomical applications: new results

Gatkine

Veilleux

et al. 2017

Opt. Express

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Abstract:One promising application of photonics to astronomical instrumentation is the miniaturization of near-infrared (NIR) spectrometers for large ground-and space-based astronomical telescopes. Here we present new results from our effort to fabricate arrayed waveguide grating (AWG) spectrometers for astronomical applications entirely in-house. Our latest devices have a peak overall throughput of ∼23%, a spectral resolving power (λ/δλ) of ∼1300, and cover the entire H band (1450−1650 nm) for Transverse Electric (TE) polarization. These AWGs use a silica-on-silicon platform with a very thin layer of Si 3 N 4 as the core of the waveguides. They have a free spectral range of ∼10 nm at a wavelength of ∼1600 nm and a contrast ratio or crosstalk of about 2% (−17 dB). Various practical aspects of implementing AWGs as astronomical spectrographs are discussed, including the coupling of the light between the fibers and AWGs, high-temperature annealing to improve the throughput of the devices at ∼1500 nm, cleaving at the output focal plane of the AWG to provide continuous wavelength coverage, and a novel algorithm to make the devices polarization insensitive over a broad band. These milestones will guide the development of the next generation of AWGs with wider free spectral range and higher resolving power and throughput.

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“…Industry uses both grating couplers and tapered couplers to achieve good performance where the latter has a better broadband response. Recently, the University of Maryland engineering and astronomy groups working together have achieved 93% buttcoupling efficiently [11] from an SMF to an SM silicon nitride (Si 3 N 4 ) waveguide using a SiO 2 on Si platform. The taper couplers are made with e-beam deposition to achieve the 100 nm features.…”

Section: Coupling and Cleaning Lightmentioning

confidence: 99%

Astrophotonics: molding the flow of light in astronomical instruments [Invited]

Bland-Hawthorn

Leon-Saval

2017

Opt. Express

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Since its emergence two decades ago, astrophotonics has found broad application in scientific instruments at many institutions worldwide. The case for astrophotonics becomes more compelling as telescopes push for AO-assisted, diffraction-limited performance, a mode of observing that is central to the next-generation of extremely large telescopes (ELTs). Even AO systems are beginning to incorporate advanced photonic principles as the community pushes for higher performance and more complex guide-star configurations. Photonic instruments like Gravity on the Very Large Telescope achieve milliarcsec resolution at 2000 nm which would be very difficult to achieve with conventional optics. While space photonics is not reviewed here, we foresee that remote sensing platforms will become a major beneficiary of astrophotonic components in the years ahead. The field has 'given back' with the development of new technologies (e.g. photonic lantern, large area multi-core fibres) already finding widespread use in other fields; Google Scholar lists more than 400 research papers making reference to this technology. This short review covers representative key developments since the 2009 Focus issue on Astrophotonics.

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Arbitrary on-chip optical filter using complex waveguide Bragg gratings

Cited by 60 publications

References 21 publications

Astrophotonic Spectrographs

Astrophotonic Spectrographs

Arrayed waveguide grating spectrometers for astronomical applications: new results

Astrophotonics: molding the flow of light in astronomical instruments [Invited]

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