“…The leading edges for the large signal regime are shown in Figure 4 b. In this section, we will present the measurements for the heating transients, but it is worth noting that both the heating (rising) and cooling (falling) processes have comparable switching times as consistent with the theory [ 31 ]. Similarly to the considerations we made in the previous sections, the rising times we measured are equivalent for all the curvature radii to a value of 29.5 ± 0.4 ms.…”
Section: Resultsmentioning
confidence: 70%
“…Dynamic response is another key performance metric for programmable circuits. While thermal isolation in general reduces both the dissipated power and the thermal crosstalk, it has been shown to have a detrimental effect on the time response of the device [ 23 , 31 ]. Rise and fall times are computed as the interval in which the signal changes from 10% to 90% and vice versa of the steady-state optical power and were assessed for both the large and small signal regime.…”
Programmability in femtosecond-laser-written integrated circuits is commonly achieved with the implementation of thermal phase shifters. Recent work has shown how such phase shifters display significantly reduced power dissipation and thermal crosstalk with the implementation of thermal isolation structures. However, the aforementioned phase shifter technology is based on a single gold film, which poses severe limitations on integration density and circuit complexity due to intrinsic geometrical constraints. To increase the compactness, we propose two improvements to this technology. Firstly, we fabricated thermal phase shifters with a photolithography process based on two different metal films, namely (1) chromium for microheaters and (2) copper for contact pads and interconnections. Secondly, we developed a novel curved isolation trench design that, along with a state-of-the-art curvature radius, allows for a significant reduction in the optical length of integrated circuits. As a result, curved Cr-Cu phase shifters provide a compact footprint with low parasitic series resistance and no significant increase in power dissipation (∼38 mW) and thermal crosstalk (∼20%). These results pave the way toward the fabrication of femtosecond-laser-written photonic circuits with a steep increase in terms of layout complexity.
“…The leading edges for the large signal regime are shown in Figure 4 b. In this section, we will present the measurements for the heating transients, but it is worth noting that both the heating (rising) and cooling (falling) processes have comparable switching times as consistent with the theory [ 31 ]. Similarly to the considerations we made in the previous sections, the rising times we measured are equivalent for all the curvature radii to a value of 29.5 ± 0.4 ms.…”
Section: Resultsmentioning
confidence: 70%
“…Dynamic response is another key performance metric for programmable circuits. While thermal isolation in general reduces both the dissipated power and the thermal crosstalk, it has been shown to have a detrimental effect on the time response of the device [ 23 , 31 ]. Rise and fall times are computed as the interval in which the signal changes from 10% to 90% and vice versa of the steady-state optical power and were assessed for both the large and small signal regime.…”
Programmability in femtosecond-laser-written integrated circuits is commonly achieved with the implementation of thermal phase shifters. Recent work has shown how such phase shifters display significantly reduced power dissipation and thermal crosstalk with the implementation of thermal isolation structures. However, the aforementioned phase shifter technology is based on a single gold film, which poses severe limitations on integration density and circuit complexity due to intrinsic geometrical constraints. To increase the compactness, we propose two improvements to this technology. Firstly, we fabricated thermal phase shifters with a photolithography process based on two different metal films, namely (1) chromium for microheaters and (2) copper for contact pads and interconnections. Secondly, we developed a novel curved isolation trench design that, along with a state-of-the-art curvature radius, allows for a significant reduction in the optical length of integrated circuits. As a result, curved Cr-Cu phase shifters provide a compact footprint with low parasitic series resistance and no significant increase in power dissipation (∼38 mW) and thermal crosstalk (∼20%). These results pave the way toward the fabrication of femtosecond-laser-written photonic circuits with a steep increase in terms of layout complexity.
“…It is worth highlighting that the measured switching times are, as expected, different from τ, due to the non-linear response of the MZI (see Eqs. 1 , 2 , 4 ) 24 . Figure 5 ( a ) Static response of the MZI at increasing values of dissipated power (standard configuration).…”
We present an optimization of the dynamics of integrated optical switches based on thermal phase shifters. These devices have been fabricated in the volume of glass substrates by femtosecond laser micromachining and are constituted by an integrated Mach–Zehnder interferometer and a superficial heater. Simulations, surface micromachining and innovative layouts allowed us to improve the temporal response of the optical switches down to a few milliseconds. In addition, taking advantage of an electrical pulse shaping approach where an optimized voltage signal is applied to the heater, we proved a switching time as low as 78 µs, about two orders of magnitude shorter with respect to the current state of the art of thermally-actuated optical switches in glass.
“…An external power supply controls the currents applied to the resistors. Dissipated power in this process induces thermal gradients in the substrate and thus locally changes the refractive index of the waveguides 48,49 . This modulates the propagation constants k i of the waveguides by the thermo-optic effect, thus allowing to change dynamically the transformation U implemented in the integrated device.…”
Section: Reconfigurable Integrated 3d Photonic Chipmentioning
Boson Sampling is a computational paradigm representing one of the most viable and pursued approaches to demonstrate the regime of quantum advantage. Recent results have shown significant technological leaps in single-photon generation and detection, leading to progressively larger instances of Boson Sampling experiments in different photonic systems. However, a crucial requirement for a fully-fledged platform solving this problem is the capability of implementing large-scale interferometers, that must simultaneously exhibit low losses, high degree of reconfigurability and the realization of arbitrary transformations. In this work, we move a step forward in this direction by demonstrating the adoption of a compact and reconfigurable 3D-integrated platform for photonic Boson Sampling. We perform 3- and 4-photon experiments by using such platform, showing the possibility of programming the circuit to implement a large number of unitary transformations. These results show that such compact and highly-reconfigurable layout can be scaled up to experiments with larger number of photons and modes, and can provide a viable direction for hybrid computing with photonic processors.
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