Athermal High-Index-Contrast Waveguide Design

Ye, Winnie N.; Michel, Jürgen; Kimerling, Lionel C.

doi:10.1109/lpt.2008.922338

Cited by 86 publications

(55 citation statements)

References 5 publications

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“…An increase of just 1 • C (which increases n ef f proportionally) can manifest as a non negligible red-shift in the resonant wavelength. By scanning the temperature from 20 • to 30 • with the TEC we found a value for this shift of dλ/dT = 71 pmK −1 , in agreement with previous studies on similar devices 29,30 . As will be seen later, this shift is comparable to the increase in λ res upon crystallization of the GST film.…”

supporting

confidence: 92%

Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials

Rudé¹,

Pello²,

Simpson³

et al. 2013

Applied Physics Letters

206

136

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A novel optical switch operating at a wavelength of 1.55 µm and showing a 12 dB modulation depth is introduced. The device is implemented in a silicon microring resonator using an overcladding layer of the phase change data storage material Ge 2 Sb 2 Te 5 (GST), which exhibits high contrast in its optical properties upon transitions between its crystalline and amorphous structural phases. These transitions are triggered using a pulsed laser diode at λ = 975 nm and used to tune the resonant frequency of the microring resonator and the resultant modulation depth of the 1.55 µm transmitted light.The ever-increasing demand for high speed optical communication networks is driving the development of new photonic devices that can process optical signals in a reliable, low-cost manner. Among competing technologies, Si-based devices have emerged as one of the main candidates for such applications, and several devices, including modulators 1-5 , add-drop filters 6 and wavelength division multiplexers (WDM) 7 have already been demonstrated. An important branch of this technology is the ability to program reconfigurable optical circuits. Indeed, a reprogrammable optical circuit that can hold its configuration without an external continuous source is extremely desirable for a multitude of applications ranging from photonic routers to optical cognitive networks. Recently, new solutions for non-volatile photonic memories have been proposed, involving the use of phase-change materials (PCM) and microring resonators 8,9 .Herein, a non-volatile Si microring resonator optical switch is demonstrated. A thin film of the phasechange material 10 (PCM) Ge 2 Sb 2 Te 5 (GST), which is commonly encountered in optical and electrical data storage applications [11][12][13][14] , is used to switch the resonant frequency and Q-factor of the microring resonator. GST shows high optical contrast between its amorphous, covalently bonded, and crystalline, resonantly bonded, structural phases 15-18 (n cryst − n amorph = 2.5 ; k cryst − k amorph = 1 at 1.55 µm) 19 . Moreover, transitions between the two phases can take place on a sub-ns timescale 20,22 while the resulting final state is stable for several years. These characteristics deem this material appropriate for application in reconfigurable optical circuits.The device, shown in Fig. 1, consists of a Si microring resonator with a bend radius of 5 µm and a coupling region of 3 µm, on top of which a GST thin film with an area of 3×1.5 µm 2 has been deposited. A second Si a) miquel.rude@icfo.es microring with identical dimensions but free of GST is used as a reference during the measurements. A 200 nm gap separates both microrings from a Si strip waveguide (220×440 nm 2 ) with grating couplers 23 at both ends, which are used to deliver light into the device and monitor the transmitted spectrum using single-mode fibers (SMF).

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supporting

confidence: 92%

Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials

Rudé¹,

Pello²,

Simpson³

et al. 2013

Applied Physics Letters

206

136

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“…Guha et al [8] and Huang et al [9] have employed alternate device design solutions to overcome the thermal dependence in interference-based devices. We have recently shown that exact athermal design is achievable for both symmetric and asymmetric waveguide-cladding geometries [10]. This communication reports the application of those design principles with the creation of prototypes that exhibit reproducible TDWS = 0.5pm/K for silicon-on-oxide ring resonators and reveal, with these devices, ultimate spectral, secondorder and footprint constraints for athermal silicon waveguides.…”

Section: Introductionmentioning

confidence: 86%

“…For an asymmetric channel waveguide system, with a different top and bottom cladding, we can express the system thermo-optic coefficient [10,11] as [11]. Henceforth, in all of our formulations, we shall consider only the effect of top cladding on the TO coefficient of the system.…”

Section: Polymer Over-claddingmentioning

confidence: 99%

Athermal operation of Silicon waveguides: spectral, second order and footprint dependencies

Raghunathan¹,

Ye²,

Juejun³

et al. 2010

Opt. Express

Self Cite

108

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Abstract:We report the design criteria and performance of Si ring resonators for passive athermal applications in wavelength division multiplexing (WDM). The waveguide design rules address i) positivenegative thermo-optic (TO) composite structures, ii) resonant wavelength dependent geometry to achieve constant confinement factor ( Γ ), and iii) observation of small residual second order effects. We develop exact design requirements for a temperature dependent resonant wavelength shift (TDWS) of 0 pm/K and present prototype TDWS performance of 0.5pm/K. We evaluate the materials selection tradeoffs between high-index contrast (HIC) and low-index contrast (LIC) systems and show, remarkably, that FSR and footprint become comparable under the constraint of athermal design.

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“…We study the tuning properties of the elastomer by measuring the transmission of a cavity in the infilled PhC as a function of temperature. Our infilled PhCs operate in another regime than athermal waveguides, 11 which are clad by a polymer with a negative TOC that exactly compensates the positive TOC of the silicon waveguide to make the properties temperature insensitive. The TOC of the elastomer, on the contrary, amply overcompensates the TOC of the PhC material, enabling thermal tuning.…”

mentioning

confidence: 99%

Tuning of a cavity in a silicon photonic crystal by thermal expansion of an elastomeric infill

Erdamar

Leest

Picken

et al. 2011

Applied Physics Letters

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We use an elastomer as infill material for a photonic crystal. As a result of the thermal-expansioninduced strongly negative thermal optical coefficient, this material is highly suitable for thermal tuning of the transmission of a cavity. This is demonstrated by global infilling of a hole-type silicon photonic crystal slab and global thermal tuning. In the temperature range 20-60 C the cavity peak shows a pronounced elastomer-induced blue shift of 2.7 nm, which amply overcompensates the red shift arising from the thermo-optic property of the silicon. These results qualify the elastomer for tuning by local optical heating. 6 and electric 7 methods, is very important for applications. Another approach is infilling the air holes of a PhC with a liquid crystal, of which the index is tuned by driving it through the phase transition. Here, we apply an elastomer as infill material to tune the transmission of a PhC cavity. Elastomers, owing to the weak bonding between the polymer chains, exhibit a strong thermal expansion and consequently a high negative thermo-optic coefficient (TOC) dn/dT. The ultimate tuning on the basis of an elastomer is by local optical heating of the elastomeric infill, by applying laser pulses, resulting in a resonancewavelength shift. Local heating can be accomplished by doping the elastomer with dye molecules or quantum dots, provided that these mainly decay non-radiatively, to ensure efficient conversion of locally deposited optical energy into heat.9 With the present experiments we qualify Kraton SEBS G 1657 10 (further just called "elastomer"), a highly stable and durable elastomer, for tuning by local heating. This is done by demonstrating global infilling of a hole-type silicon PhC slab with the elastomer and global thermal tuning of its refractive index. We study the tuning properties of the elastomer by measuring the transmission of a cavity in the infilled PhC as a function of temperature. Our infilled PhCs operate in another regime than athermal waveguides, 11 which are clad by a polymer with a negative TOC that exactly compensates the positive TOC of the silicon waveguide to make the properties temperature insensitive. The TOC of the elastomer, on the contrary, amply overcompensates the TOC of the PhC material, enabling thermal tuning.The PhCs are fabricated in silicon-on-insulator (SOI) material. The device layer is 220 nm thick; the buried oxide is 2 lm thick. The lithographic pattern is written in ZEP 520 resist with an e-beam writer and is transferred to the silicon using plasma etching in an SF 6 -based plasma. Membrane PhCs result from underetching the patterned silicon. The PhCs have a triangular lattice with nine rows of holes between 2.5 lm wide waveguides and are oriented for light propagation in the CM direction. The designed ratio r/a of the hole radius to the lattice constant is 0.3, while a is lithotuned in the range 490-510 nm. Having measured the empty crystal (i.e., holes not infilled), the chip is cleaned to prepare for infilling, which is done by applying a drople...

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Athermal High-Index-Contrast Waveguide Design

Cited by 86 publications

References 5 publications

Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials

Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials

Athermal operation of Silicon waveguides: spectral, second order and footprint dependencies

Tuning of a cavity in a silicon photonic crystal by thermal expansion of an elastomeric infill

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