Low-loss chalcogenide waveguides on lithium niobate for the mid-infrared

Abstract

We demonstrate low-loss chalcogenide (As(2)S(3)) waveguides on a LiNbO(3) substrate for the mid-IR wavelength (4.8 μm). Designed for single-mode propagation, they are fabricated through photolithography and dry-etching technology and characterized on a mid-IR measurement setup with a quantum cascade laser. For straight waveguides, propagation loss as low as 0.33 dB/cm is measured and low-loss bends on the order of 100 μm are simulated, with measurement results showing <3 dB for a 250 μm bend radius. The coupling efficiency is estimated to be 81%. In addition, the influences of variations in width and bend radius are also investigated.

Solution-processed chalcogenide glass for integrated single-mode mid-infrared waveguides

“…Recently, mid-IR waveguides have been demonstrated using several different fabrication approaches. For example, laser writing is used to produce single mode channel waveguides for λ = 8.4µm in As 2 Se 3 films deposited by thermal evaporation [13], while reactive-ion etching is used to pattern strip waveguides in sputter-deposited As 2 S 3 films [14]. In our prior work, a solution-casting and molding process using a soft lithography method called micro-molding in capillaries (MIMIC) [15,16], is employed to form multi-mode As 2 S 3 strip waveguides [17].…”

“…Substrate material choice is important since the absorptiveness of the substrate will have a large effect on waveguide loss [17]. Low loss substrate possibilities include lithium niobate (LiNbO 3 ) [14] or sapphire wafers for λ < 5µm, and salt crystals [17] or other chalcogenide materials [13,18] for longer wavelengths. In addition, compared to waveguides for shorter wavelengths, mid-IR waveguide dimensions will be in the 2-10µm range, which can make mechanical stress a concern in thin film deposition processes.…”

Demonstration of high-Q mid-infrared chalcogenide glass-on-silicon resonators

“…Besides their excellent mid-IR transparency, ChGs possess low thermal conductivity (<1 W∕mK, large thermo-optic coefficients (>10 −4 ∕K), and hence a photothermal figure-of-merit >300 times higher than silicon, making them ideal material candidates for on-chip photothermal detection down to single chemical molecule levels [8,9]. ChG mid-IR waveguides have been fabricated on silicon using photosensitive writing [10] and on exotic substrates, such as As 2 S 3 glass [11], NaCl [12,13], and LiNbO 3 [14]. However, mid-IR ChG resonators have not yet been demonstrated.…”

Beam combination schemes and technologies for the Planet Formation Imager

“…Single-and multi-mode channel waveguides have been demonstrated. 50,51 • (CW-and ultrafast) laser writing is a recent but promising technique relying on the use of ultrashort laser pulses to directly inscribe three-dimensional waveguide structures inside a transparent glass substrate. Ultrafast laser writing provides the ability to fabricate waveguide crossings with zero cross-talk and beam combiners based on two-dimensional arrays of coupled waveguides (DBC, see previous section).…”