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(a) Optical micrograph image of an As 2 S 3 planar waveguide cleaved facet. Numerical results showing (b) fundamental TM mode intensity profile and (c) group velocity dispersion of TM, TE mode and material dispersion for a 2 µm width planar waveguide.
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We demonstrate chip-based Tbaud optical signal processing for all-optical performance monitoring, switching and demultiplexing based on the instantaneous Kerr nonlinearity in a dispersion-engineered As(2)S(3) planar waveguide. At the Tbaud transmitter, we use a THz bandwidth radio-frequency spectrum analyzer to perform all-optical performance monit...
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... key device in these monitoring and demultiplexing experiments is a 7 cm long dispersion engineered As 2 S 3 planar waveguide whose micrograph image and characteristics are shown in Fig. 2. Details of the fabrication of this As 2 S 3 planar waveguide have been described in [28,29]. In order to offset the large material dispersion of about -370 ps/nm/km, the As 2 S 3 film thickness was reduced to ~0.85 µm resulting in a combined waveguide and material dispersion of ~29 ps/nm/km for the transverse-magnetic (TM) mode at ...
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... 2. Details of the fabrication of this As 2 S 3 planar waveguide have been described in [28,29]. In order to offset the large material dispersion of about -370 ps/nm/km, the As 2 S 3 film thickness was reduced to ~0.85 µm resulting in a combined waveguide and material dispersion of ~29 ps/nm/km for the transverse-magnetic (TM) mode at 1550 nm [ Fig. 2(c)]. The nonlinear coefficient γ of this waveguide at a wavelength of 1550 nm was therefore enhanced up to ~9900 /W/km. The optical micrograph and the numerical intensity mode profile of the TM mode are shown in Fig. 2(a) and 2(b). This short and low dispersion waveguide offers very low walk-off, thus enabling high measurement accuracy ...
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... µm resulting in a combined waveguide and material dispersion of ~29 ps/nm/km for the transverse-magnetic (TM) mode at 1550 nm [ Fig. 2(c)]. The nonlinear coefficient γ of this waveguide at a wavelength of 1550 nm was therefore enhanced up to ~9900 /W/km. The optical micrograph and the numerical intensity mode profile of the TM mode are shown in Fig. 2(a) and 2(b). This short and low dispersion waveguide offers very low walk-off, thus enabling high measurement accuracy and excellent FWM conversion efficiency. ...
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... N onlinear optics mainly involves the phenomena and laws produced by the interaction between strong coherent light and matter, 1) which plays a crucial role in promoting the development of ultrafast spectrum, 2) information processing, 3,4) communications security 5,6) and medical diagnosis. 7) However, the nonlinearity of materials is generally perturbative, which is inherently a weak effect. ...
The excitation wavelength dependent nonlinear optical response of fluorine-doped tin oxide (FTO) is systematically studied by the Z-scan technique. The broadband third-order nonlinear optical properties of FTO are verified and a value of nonlinear refractive index n2 to be 2.52×10-16 m2/W is obtained at epsilon-near-zero (ENZ) region. Meanwhile, a large modulation depth and nonlinear absorption coefficient β is estimated about 9.61% and -1.96×10-9 m/W, respectively. The experimental results indicate that FTO is a promising nonlinear optical material and has great application potential in the field of nonlinear optical devices.
... (e) reflection spectra of "writing" and "erasing" selected mode in As 2 S 3 microcavity based on photoinduced refractive index variation [137] (upper image is reflection spectrum including three modes, lower left image is reflection spectrum of three modes after erasing mode 2, lower middle image is local reflection spectrum before erasing mode 2, and lower right image is local reflection spectrum after erasing mode 2) Fig. 9 Hybrid integrated ChGbased devices. (a) ChG and lithium niobate hybrid integrated microring modulator and MZI modulator [139] ; (b) As 2 S 3 vertically integrated optical phased array on lithium niobate substrate [141] ; (c) acoustooptic modulator with lithium niobate/GeSbS hybrid integrated MZI structure [144] ; (d) GeSbSe waveguide integrated black phosphorus photodetector [147] ; (e) hybrid integrated photodetector based on ChG waveguide and tellurene [148] 封面文章·特邀综述 第 42 卷 第 23 期/2022 年 12 月/光学学报 Fig. 10 ChG waveguides and systems for alloptical signal processing [154] . (a) Cross section of As 2 S 3 planar waveguide; (b) simulated group velocity dispersion of TE and TM modes and material dispersion of onchip waveguide; (c) principle diagrams of transmitter optimization of Tbit/s bandwidth signal and demultiplexing time division multiplexing signal receiver system 封面文章·特邀综述 第 42 卷 第 23 期/2022 年 12 月/光学学报 Fig. 12 Results of ChG integrated microresonators in optical frequency comb applications [53,67] . ...
... The values of n 2 and β [29] can be extracted from the closedaperture and the open-aperture curves, respectively. The results at the telecommunications wavelength [30,31] are shown in Figs. 2(b) and 2(c), where the discrete points represent the test data and the solid lines depict fitting results. ...
An on-chip supercontinuum (SC) source spanning from 900 nm to 2000 nm has been experimentally presented and analyzed based on a ${\rm{G}}{{\rm{e}}_{11.5}}{\rm{A}}{{\rm{s}}_{24}}{{\rm{S}}_{64.5}}$ G e 11.5 A s 24 S 64.5 (GeAsS) planar waveguide at telecommunication wavelength. The nonlinear response parameter ( $\gamma$ γ ) of the GeAsS waveguide is estimated to be ${\sim}{{12}}\;{\rm{/W/m}}$ ∼ 12 / W / m at the pump wavelength using resonant grating waveguide (RGW) nonlinear refractive index ( ${{\rm{n}}_2} = {{2}} \times {{1}}{{{0}}^{- 18\:}}{{\rm{m}}^2}/{\rm{W}}$ n 2 = 2 × 1 0 − 18 m 2 / W ), which is measured by the z-scan technique. The dispersion of the waveguide is carefully engineered based on the refractive index of the GeAsS film where the film structure is confirmed by a Raman spectrum exhibiting consistency with the corresponding glass. The results suggest that the GeAsS glass is expected to be an ideal platform for on-chip devices.
... ChG films can be flexibly deposited on substrates such as silicon, silica, and polymers by physical vapor deposition techniques and patterned by a CMOS-compatible process to form various photonic structures such as rib/strip waveguides [16], microdisks [17], microrings [18,19], and photonic crystals [20,21]. FWM has been extensively studied in ChG waveguides fabricated with different compositions, and applications such as wavelength conversion [22], thirdharmonic generation [20], all-optical demultiplexing [23], and photon pair generation [21] have been demonstrated. However, to the best of our knowledge, FWM has not been demonstrated with on-chip ChG microresonators to date. ...
A compact ${{\rm Ge}_{11.5}}{{\rm As}_{24}}{{\rm Se}_{64.5}}$ G e 11.5 A s 24 S e 64.5 chalcogenide microring resonator is fabricated with an intrinsic quality factor of $3.0 \times {10^5}$ 3.0 × 10 5 in the telecom band. By taking advantage of the strong nonlinearity and cavity enhancement, highly efficient wavelength conversion via four-wave mixing is demonstrated using a microring resonator. Conversion efficiency of ${-}33.7\; {\rm dB}$ − 33.7 d B is obtained by using an ultra-low pump power of 63.8 µW. This work shows that ${{\rm Ge}_{11.5}}{{\rm As}_{24}}{{\rm Se}_{64.5}}$ G e 11.5 A s 24 S e 64.5 chalcogenide microring devices are promising for quantum photonics.
... Many research endeavors have focused on the quest for materials with strong and fast nonlinear light-matter interactions. Large ultrafast nonlinear optical responses are paramount for a plethora of applications relying on active photonic integrated circuits, ranging from alloptical signal processing [1,2] to quantum computers [3,4]. But the integration density of these devices, if based on nonresonant nonlinear processes (hinging upon virtual transitions and ergo very fast), is burdened by the intrinsic perturbative nature of such nonlinear phenomena, which typically require high optical intensities and/or long interaction lengths. ...
... where the second-order nonlinear optical susceptibility is denoted by χ (2) . By placing Eqs. ...
... is fixed (moreover, for small ζ, given that tanh(ζ) ≈ ζ, the intensity and amplitude conversion efficiencies scale with η 3 and η, respectively). This behavior can be seen in Fig. 1, which shows the evolution of u 2 2 vs. distance (normalized with respect to the wavelength of the fundamental frequency in vacuum λ) for χ (2) ...
We investigate, theoretically and numerically, the dependence of a material's nonlinear-optical response on the linear relative electric permittivity $\epsilon$ and magnetic permeability $\mu$. The conversion efficiency of low-order harmonic-generation processes, as well as the increase rate of Kerr-effect nonlinear phase shift and nonlinear losses from two-photon absorption (TPA), are seen to increase with decreasing $\epsilon$ and/or increasing $\mu$. We also discuss the rationale and physical insights behind this nonlinear response, particularly its enhancement in $\epsilon$-near-zero (ENZ) media. This behavior is consistent with the experimental observation of intriguingly high effective nonlinear refractive index in degenerate semiconductors such as indium tin oxide [\textit{Alam et al., Science 352 (795), 2016}] (where the nonlinearity is attributed to a modification of the energy distribution of conduction-band electrons due to laser-induced electron heating) and aluminum zinc oxide [\textit{Caspani et al., Phys. Rev. Lett. 116 (233901), 2016}] at frequencies with vanishing real part of the linear permittivity. Such strong nonlinear response can pave the way for a new paradigm in nonlinear optics with much higher conversion efficiencies and therefore better miniaturization capabilities and power requirements for next-generation integrated nanophotonics.
... ChGs have wide application potential in optical device, photonics and telecommunication technologies such as night vision, mid-IR sensor, and waveguide hologram since they have outstanding properties such as remarkable infrared transparency and transmission range, high refractive index high photosensitivity, and low transmission loss [1][2][3][4]. Among a variety of ChGs, the ternary Ge-Sb-Se glasses are attractive candidates for optical-grade lenses and filters as well as infraredtransmitting optical fibers and waveguides [5][6][7][8][9][10] due to their high mechanical and thermal stability, high refractive indices, ultrafast optical response as well as superior infrared transmission range of 900 nm-16 μm and good infrared transmittance (above 60%) [11][12][13][14]. In addition, Ge-Sb-Se glasses are less toxic and thus more environmentally-compatible. ...
... In addition to the switching time, the repetition rate is another important feature for optical processing. For example, four-wave mixing devices have demonstrated timedomain mutiplexing at Tbit s −1 repetition rates at an energy cost with picojoule range 45,46 . Although we have not performed multiple-pulse experiments at present, we expect that graphene is also promising for achieving ultrafast repetition rates, because the reported values of the carrier recombination lifetime are mostly around a few picoseconds or less 24,[47][48][49] . ...
All-optical switches have attracted attention because they can potentially overcome the speed limitation of electric switches. However, ultrafast, energy-efficient all-optical switches have been challenging to realize owing to the intrinsically small optical nonlinearity in existing materials. As a solution, we propose the use of graphene-loaded deep-subwavelength plasmonic waveguides (30 × 20 nm2). Thanks to extreme light confinement, we have greatly enhanced optical nonlinear absorption in graphene, and achieved ultrafast all-optical switching with a switching energy of 35 fJ and a switching time of 260 fs. The switching energy is four orders of magnitude smaller than that in previous graphene-based devices and is the smallest value reported for any all-optical switch operating at a few picoseconds or less. This device can be efficiently connected to conventional silicon waveguides and used in silicon photonic integrated circuits. We believe that this graphene-based device will pave the way towards on-chip ultrafast and energy-efficient photonic processing. All-optical switching with a switching energy of 35 fJ and a switching time of 260 fs is reported in a nanoscale integrated optical circuit.
... In addition to the switching time, the repetition rate is another important feature for optical processing. For example, four-wave mixing devices have demonstrated time-domain mutiplexing at Tbit/s repetition rate for at an energy cost with pico-joule range45,46 . Although we have not done multiple-pulse experiments at present, we expect that graphene is promising also for ultrafast repetition rate because the reported values of the carrier recombination lifetime are mostly around a few ps or less24,[47][48][49] . ...
All-optical switches have attracted attention because they can potentially overcome the speed limitation of electric switches. However, ultrafast, energy-efficient all-optical switches have been challenging to realize due to the intrinsically small optical nonlinearity in existing materials. As a solution, we propose graphene-loaded deep-subwavelength plasmonic waveguides (30 nm x 20 nm). Thanks to extreme light confinement, we have significantly enhanced optical nonlinear absorption in graphene, and achieved ultrafast all-optical switching with a switching energy of 35 fJ and a switching time of 260 fs. The switching energy is four orders of magnitudes smaller than that in previous graphene-based devices and is the smallest value ever reported for any all-optical switch operating at a few picoseconds or less. This device can be efficiently connected to conventional Si waveguides and employed in Si photonic integrated circuits. We believe that this graphene-based device will pave the way towards on-chip ultrafast and energy-efficient photonic processing.
... [2][3][4][5][6] In addition, the high material nonlinearity of GST, combined with the strong connement and dispersion in ber and waveguide devices, makes it attractive for fast nonlinear optical devices. 7,8 However, there are also some deciencies in the performance of GST, especially its relatively large optical nonlinear absorption in the optical communication band and poor chemical and thermal stability. 9,10 Nowadays, phase change materials (PCMs) are the focus of scientic research. ...
In this work, phase change chalcogenide Ge2Sb2Te5 (GST) thin films were fabricated by magnetron sputtering. The optical properties, especially the optical constants (refractive index and extinction coefficient), of such alloys were systematically studied by investigating their thermally and photo-thermally induced switching between different phases. The results show that GST films are highly tunable in microstructure and optical constants, either by post-annealing at 160 °C, 200 °C, 250 °C and 350 °C, respectively, or by laser irradiation of 1 mW, 3 mW, 5 mW and 10 mW power with beam diameter of 7 μm at 532 nm, respectively. From the structural analysis, we can clearly observe different crystallinities and chemical bonding in the different post-treated GST films. The optical constants of GST films under various phases were obtained from spectrophotometry, by fitting their transmittance data with the Tauc–Lorentz (TL) dispersion model. The refractive index and extinction coefficient exhibit notable change upon annealing and laser irradiation, specifically at 1550 nm, from 3.85 (amorphous) to 6.5 (crystalline) in refractive index. The optical constants have been proved capable of fine tuning via the laser irradiation method. Hence, the pronounced adjustability in optical properties due to rapid and repeatable phase change render GST suitable for tunable photonic devices.
... 19 It enables the extraordinarily large nonlinearity to be realized only using relatively short pieces of fiber. Many mid-IR photonic devices, including supercontinuum (SC) sources, 20 fiber laser, 21 fiber sensor, 22 fiber coupler/attenuator, 23,24 all optical wavelength converters, 25 and correlated photon-pair generator, 26 have been proposed using dispersion engineered chalcogenide fibers. However, as far as we know, the mid-IR high birefringence PCFs are seldom reported until now. ...
A midinfrared high birefringence Ge20Sb15Se65-based hexagonal lattice photonic crystal fiber (PCF) with central defect core and dual-rhombic air holes cladding is proposed. The finite difference time-domain method with perfectly matched layer absorption boundary conditions are used to numerically analyze the guided modes of the designed PCF. The properties of this PCF including the birefringence, beat length, dispersion, and nonlinearity are investigated in the 3 to 5 μm midinfrared range. The results show that for the optimized structure parameters of Λ A = 2 μm, D = 1.7 μm, H = 1.76, and d = 0.4 μm, the highest birefringence of 0.1513 and beat length of 33.04 μm are obtained. The maximum nonlinearity coefficients of 3726 and 2585 w⁻¹ km⁻¹ for x- and y-polarization modes are achieved. The distinctive dispersion is acquired, which is all-normal for x-polarization mode while has single zero dispersion points at 3.96 μm for y-polarization mode. The designed PCF will have broad application in midinfrared optical fiber sensing, nonlinear optics, and precision optical instruments. © 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).
