Integrated photonic materials for the mid‐infrared

Abstract

While silicon photonic integrated circuits for the near-infrared (IR) telecommunication band have attracted great research interest in the past decade, recent advances offer opportunities to extend the operational wavelength to the mid-IR (2.5-20 μm) for free space communications, sensing, environmental monitoring and much more.In this study, we will comprehensively review the current status of materials available for mid-IR waveguides and waveguide integrated photodetectors, with a few application oriented examples to illustrate the technological importance and significant growth opportunity for integrated photonics in the mid-IR regime. However, this wavelength regime also presents new material design and fabrication challenges.Therefore, we will discuss the critical issues prior to commercialization and will briefly summarize the outlook on future research topics along with opportunities.

Integrated Nanophotonic Waveguide-Based Devices for IR and Raman Gas Spectroscopy

“…Nevertheless, a wide range of other materials has been reported, including polymers (i.e., photoresists and Teflon) [57], halides, chalcogenides (i.e., CaF2, NaBr and ZnSe) [28,58], oxides (i.e., alumina, titania and tantala) [59,60], diamond (due to its advantages for quantum photonics) [61,62], or InGaAs [63]. Recently, a review on waveguide materials has been published by Yadav and Agarwal [64].…”

“…Among chip-integrated single-pixel detectors, group IV materials like silicon or germanium or a combination of III-V materials, such as InGaAs, InGaAsSb, InAsSb, PbTe, GaSb, and InP have been used as platforms for NIR and MIR sensing [64,65]. While Si can only absorb up to about 1.1 µm, ion implantation or introducing lattice defects or external agents can improve the detection range of Si-based photodetectors up to 2.4 µm [64]. The entire MIR spectral range can be covered by mercury cadmium telurite (MCT) detectors, which are also most widely used for MIR sensing in bulk spectrometers.…”

Structure and mid-infrared optical properties of spin-coated polyethylene films developed for integrated photonics applications

“…In a first integration step, both can be combined into specifically tailored devices with same-wavelength emission and detection from the same active region 13,17,18 , paving the way for a new class of monolithic photonic integrated circuits (PICs) 6,19 . However, in contrast to near-IR PICs with their high degree of maturity 20 , mid-IR (2-20 µm) PICs are still in the early stages of development 21 , and implementing existing integrated photonics solutions remains a challenging task 21,22 . It includes the requirement for new materials 23 and advanced fabrication schemes for developing low-loss and low-dispersion LWIR passive photonic structures on the chiplevel.…”

Waveguide-Integrated Mid-Infrared Photodetection using Graphene on a Scalable Chalcogenide Glass Platform

“…However, integrating the detector on-chip is more compact and can improve sensitivity by reducing the volume of active material able to generate thermal noise. Su et al achieved integration of a PbTe photoconductor and demonstrated methane sensing at a wavelength of λ = 3.31 µm [5], but their platform is limited to λ 4 µm due to absorption in the SiO 2 substrate [6] and by PbTe's absorption cutoff [7]. Waveguide-integrated detectors based on narrow-gap 2D materials black phosphorus [8] and tellurene [9] have also been demonstrated, but they too are bandgap-limited to λ 4 µm.…”

“…While graphene integrated detectors have shown promise at telecom wavelengths [10], the material's advantages are magnified further at longer wavelengths due to the thermal nature of the photothermoelectric (PTE) response mechanism [11,12] and due to the impact of optical plasmon scattering at short wavelengths [13]. Integrated photodetection with graphene has been demonstrated at wavelengths up to 3.8 µm [6] and with chalcogenide glass waveguides [14], but on SiO 2 platforms. To access longer wavelength operation and achieve good sensitivity at zero bias, we introduce a Ge 28 Sb 12 Se 60 (GSSe)-on-CaF 2 waveguide platform supporting gated PTE-based graphene photodetectors.…”