Grating-coupled silicon-on-sapphire integrated slot waveguides operating at mid-infrared wavelengths

Abstract

We demonstrate subwavelength bidirectional grating (SWG) coupled slot waveguide fabricated in silicon-on-sapphire for transverse electric polarized wave operation at 3.4 μm wavelength. Coupling efficiency of 29% for SWG coupler is experimentally achieved. Propagation loss of 11 dB/cm has been experimentally obtained for slot waveguides. Two-step taper mode converters with an insertion loss of 0.13 dB are used to gradually convert the strip waveguide mode into slot waveguide mode.

Mid-infrared integrated photonics on silicon: a perspective

“…Table 1 shows the available passive platforms for mid-IR integrated photonics on Si, including the best reported results on low loss performance obtained in each category. Although silicon-on-sapphire (SOS) [44][45][46][47][48][49][50][51] is not formed on a Si substrate, it is widely adopted for mid-IR photonics and is also included for comparison.…”

Mid-infrared holey and slotted photonic crystal waveguides in silicon-on-sapphire for chemical warfare simulant detection

“…The design and characterization of SWGs used here has been described in detail before [7]. As in previous research [12,14,15], a PC group index taper is implemented at the input and output interfaces of the holey PCW with the strip waveguide to reduce Fresnel reflection losses and enhance light coupling efficiency into the slow light guided mode.…”

“…We also demonstrated slot waveguides in the mid-IR in SoS [7]. Recently, we provided the first demonstration of PCW characteristics in SoS at the mid-IR wavelength 3.43 m with a fixed wavelength interband cascade laser (ICL) [12].…”

“…Another platform in Silicon on nitride (SON), demonstrated by Khan et al [6] has a transparency window that extends to 6.7 m; however the higher refractive index of cladding silicon nitride (n > 2, depending on silicon fraction) compared with sapphire (n∼1.7) also reduces the available photonic band gap in PC structures. Furthermore, at ∼3.4 m, SON waveguides are also more lossy (5.2 dB/cm) [6] compared to SoS ridge waveguides (2.1 dB/cm) [7]. Thus SoS provides an ideal platform for PC-based mid-IR photonic sensors till 5.5 m. PC research in the mid-IR has however been limited by the need for bulky and expensive tunable laser sources [8,9] that made it conceivably difficult to transition PC sensors from the lab to the field.…”

Polymer waveguides self-organized by two-photon photochemistry for self-aligned optical couplings with wide misalignment tolerances

“…To date, edge couplings with mode converters [21] and grating couplings with tapered waveguides [14,[22][23][24] have been developed. The former enables low-loss inplane couplings with a loss smaller than 1 dB, and the latter enables low-loss vertical couplings.…”