We propose and numerically analyze the hybrid Si-Ge 2 Sb 2 Te 5 strip waveguide switches for Mid-IR wavelength of 2.1 µm. The switches investigated are one input-one output (on-off) type and one input-two outputs (directional coupler) type. The reversible transition between the switch states is achieved by inducing the phase transition from crystalline to amorphous and vice-versa by application of voltage pulses. The approach of embedding the nanoscale active material Ge 2 Sb 2 Te 5 within the Si waveguide is taken to enhance the interaction of light with the active region of the switches. The dimensions of the active regions of the switches are optimized to achieve low insertion loss, low switching energy and high extinction ratio. In case of one input-one output switch, an extinction ratio of 33.79 dB along with an extremely low insertion loss of 0.52 dB is achieved using optimum Ge 2 Sb 2 Te 5 length of only 0.92 µm. For one input-two outputs switch, an extinction ratio of 10.33 dB and 5.23 dB is obtained in cross and bar state respectively using an active length of 52 µm. These values of extinction ratio, which are otherwise 18.59 dB and 8.33 dB respectively, are due to the necessity of doping the Si beneath the Ge 2 Sb 2 Te 5 to facilitate the electrical conduction needed for Joule heating. A suitable gap of 100 nm is kept between the active and passive arm of the directional coupler switch. The electro-thermal co-simulations confirm that phase change occurs in whole of the Ge 2 Sb 2 Te 5 region in both types of switches.

We report design of a high static performance on-off optical switch using nanoscale phase change material G e 2 Sb 2 Te 5 embedded into silicon-on-insulator waveguide. This active material can be switched between amorphous and crystalline states using electrical/optical pulses. The fundamental mode propagating through Silicon waveguide drastically alters its properties due to high index change at Si − G e 2 Sb 2 Te 5 interfaces and absorption in G e 2 Sb 2 Te 5 . The optical switch made of Silicon waveguide with G e 2 Sb 2 Te 5 of volume 400 nm × 180 nm × 450 nm (length × height × width) embedded in to it, provides high extinction ratio of 43 dB with low insertion loss of 2.76 dB in ON state at communication wavelength of 1550 nm. There is trade-off between insertion loss and extinction ratio. For 10 dB extinction ratio, The insertion loss can be as low as 1.2 dB and corresponding active volume is also pretty low (100 nm × 150 nm × 450 nm (length × height × width)). Further, spectral response investigations reveal that this switch maintains extinction ratio more than 30 dB in wavelength span 1500-1600 nm. The high static performance of optical switch reported here is a direct result of proper dimensional engineering of active volume as well as its incorporation into the silicon-on-insulator waveguide. We also propose figure-ofmerit for non volatile optical switches that takes into account relevant parameters of static performance.

Phase change material G e 2 S b 2 T e 5 (GST) has recently emerged as a highly promising candidate for photonic device applications owing to its high optical contrast, self-holding bi-stability, and fast material response. Here, we propose and analyze a 1 × 2 tunable switch using a GST embedded silicon microring resonator exploiting high optical contrast during GST phase change and a high thermo-optic coefficient of amorphous phase GST. Our device exhibits high extinction ratios of 25.57 dB and 18.75 dB at through and drop ports, respectively, with just a 1 µm long GST layer. The two states of the switch are realizable by electrically inducing phase change in GST. For post phase change from amorphous to crystalline and vice versa, the fall time down the 80% of phase transition temperature is ∼ 66 n s and ∼ 45 n s , respectively. The resonance wavelength shift per unit active length is 0.661 nm/µm, and the tuning efficiency is 1.16 nm/mW. The large wavelength tunability (4.63 nm) of the proposed switch makes it an attractive option for reconfigurable photonic integrated circuits.

We report thorough investigations of a photonic memory with phase change material embedded in a partially etched silicon waveguide, for operation at 1550 nm wavelength. Optical and thermal analyses are performed to study the performance of memory and the effect of deformity in G e 2 S b 2 T e 5 (GST) cells due to volume contraction upon crystallization. The presented approach has better performance than other approaches with GST integrated on top of or filled in a fully etched waveguide. It is shown that a high readout contrast of ∼ 33 d B with a low insertion loss of 0.79 dB is possible using an active volume of only 0.0079 µ m 3 . The photonic memory presented shows a low power consumption of 0.66 mW and 3.71 mW for switching the memory state from high to low and vice versa, respectively, with zero static power consumption. Using 100 ns and 10 ns pulses for phase transformation from amorphous to crystalline and that from crystalline to amorphous, the energy consumption is 82 pJ and 44.1 pJ, respectively.

No abstract