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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Chalcogenide Glass Polarization-Maintaining Photonic Crystal Fiber for Mid-Infrared Supercontinuum Generation
摘要： Chalcogenide-glass-based optical fibers are excellent photonic platforms for nonlinear applications in the mid-IR region due to their wide transmission window, tunable dispersion and high optical nonlinearity. There is particular interest in combining the chalcogenide fiber platform with polarization-preserving properties as this will allow polarization-dependent measurements while minimizing detrimental effects and thus enable new applications in interferometric techniques, gas sensing, integrated-optic devices and optical coherence tomography. In this work, for the first time to our knowledge, we demonstrate mid-IR supercontinuum (SC) generation in a highly birefringent polarization maintaining photonic crystal fiber (PM-PCF). The PM-PCF was drawn using the casting method from As38Se62 glass which features a transmission window from 2-10 μm and a high nonlinear refractive index up to 1.13×10-17 m2/W [1,2]. To introduce strong birefringence, an asymmetric arrangement of air holes was used as shown in Fig. 1(a). The PCF cross section consists of 36 circular air holes in 3 rings with 2 larger air holes adjacent to the core. The (approximate) core diameter (i.e. distance between two large air holes) is ~8.1 μm and the outer diameter of the PCF is 125 μm. The group velocity dispersion and group birefringence for the fundamental mode (computed from the SEM image) are shown in Fig. 1(b). The fiber has a zero-dispersion wavelength around 4.5 μm and, at this wavelength, a large birefringence of 6×10-4 such that strong polarization maintaining properties are expected. In our experiments, a 25cm long PM-PCF was pumped with 250 fs pulses at 4 μm (i.e. the normal dispersion regime) using the same experimental setup for MIR SC generation as previously described in Ref. [3]. Figure 1(c) shows the generated SC spectra with different output power. For a pump power of 135 mW, we obtained a SC spectrum from 3.1-6.02 μm with an average output power of 11 mW. Pumping close to the zero dispersion wavelength with the pump at 4.53 μm yielded comparable spectral broadening but at much lower input pump power of 62 mW as shown in Fig. 1(d). In this case, we were able to measure the polarization dependence of the SC spectra by changing the coupling angle through rotation of the fiber. These results demonstrate the potential of chalcogenide PM-PCF for polarized SC generation, and work is underway to optimize the spectral generation and polarization dependency using detailed numerical modelling.
关键词： Polarization-maintaining,Photonic crystal fiber,Chalcogenide glass,Mid-infrared,Supercontinuum generation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photoreduction in Optofluidic Hollow-Core Photonic Crystal Fiber
摘要： Optofluidic hollow-core photonic crystal fiber (HC-PCF) uniquely allows light to be guided at the centre of a microfluidic channel. The system maximizes the interaction of light with infiltrated chemicals and (nano)particles, offering unique opportunities for in-situ optical monitoring of a range of photochemical and catalytic reactions [1,2]. Our current goal is to extend this work to hybrid colloidal systems comprising a particulate light absorber and a molecular catalyst for photocatalytic fuel production [3]. Here we use HC-PCF microreactors to study novel light-absorbing particles for such systems: graphitic, N-doped, and amorphous carbon-nanodots (CNDs) that offer a unique combination of scalability, biocompatibility, water solubility, and stable optical properties [4]. To test the CNDs’ absorption- and electron-transfer properties, we combine them with the redox-active heterocycle methyl viologen dichloride (MV2+·2Cl-). Upon absorption of UV light, CNDs can transfer an electron to MV2+, whose reduction to the radical cation (MV?+) creates a strong optical absorption peak around 600 nm (Figs. 1(a,c)). An electron donor (EDTA) is added to the solution to quench the photo-induced holes in the CNDs [4]. The mixture was infiltrated into the core of a 30 cm long liquid-filled kagomé style HC-PCF (Fig. 1(b)), designed to guide in the wavelength range of the MV?+ absorption peak. To ensure a homogeneous excitation of the CNDs, a 5 cm long section of the fiber was side-illuminated by a UV lamp (λ = 365 nm). A supercontinuum source, launched into a guided mode, was used to monitor the absorption spectrum. Despite sample volumes of less than 50 nL, we obtain highly-reproducible time traces of the MV?+ absorption (Fig 1(d-e)). Unexpectedly, a significant initial time-delay of 135 s was observed in the reduction of MV2+, revealing the presence of a previously unknown activation process of the CNDs. The initial delay was found to depend on the functionalization of the CNDs, with delays for a -COOH group (81 s) being ca. three times shorter than those for NH2 (176 s) and NMe2 (204 s) groups. The subsequent reaction rate was found to be independent of the surface-group. Our unexpected results highlight the scope for urgently needed in-situ analysis of photocatalytic systems. Future experiments will include the use of surface-sensitive higher-order modes [5] to selectively probe the diffusion of reaction products within the optofluidic reactor.
关键词： Carbon-Nanodots,Photoreduction,Hollow-Core Photonic Crystal Fiber,Optofluidic,Photocatalytic
更新于2025-09-12 10:27:22
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An integrable all-silicon slotted photonic crystal Raman laser
摘要： The design of an integrable all-silicon Raman laser of a foot print of (cid:1)7 μm is proposed based on a slotted photonic crystal nanocavity. The slot has been considered to be made of a silicon nanocrystal to encash its giant Raman gain coe?cient, along with the tight spatial and temporal con?nement of light in the slot, exhibiting a lasing e?ciency of (cid:1)17:8% at a wavelength of 1552 nm. Simulations depict that the device requires a very small optical threshold power of the order of 0.5 μW. Tolerances to the fabrication imperfections have also been evaluated, which explores that the device performance is tolerant up to a 6% random deviation in structural parameters like radius and in-plane positions of the holes. It has also been seen through simulations that the submicrowatt threshold is maintained even for a large deterioration of over 30% in the Q-factors and modal volumes, which reassures the realization feasibility of the device.
关键词： fabrication tolerance,photonic crystal nanocavity,silicon nanocrystal,lasing efficiency,all-silicon Raman laser
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Soliton Self-Compression and UV Dispersive Wave Emission in Compact Hollow Capillary Systems
摘要： Soliton dynamics underlie a wide range of phenomena in nonlinear fibre optics. In particular, higher-order solitons in gas-filled hollow-core photonic crystal fibre (HC-PCF) have been applied to self-compression of ultrafast laser pulses [1] and the generation of widely tuneable resonant dispersive waves (RDW) from the vacuum ultraviolet (VUV) to the visible spectral range [2]. We recently demonstrated that by moving to long, large-core hollow capillary fibres (HCF) and shorter driving pulses, these effects can be scaled by up to three orders of magnitude in pulse energy, providing unprecedented peak power in ultrafast VUV pulses as well as a route towards terawatt-scale optical attosecond pulses [3]. Here we show that by further decreasing the initial pulse duration, high-energy soliton dynamics can be obtained in HCF as short as 35 cm.
关键词： Soliton dynamics,ultrafast laser pulses,hollow-core photonic crystal fibre,nonlinear fibre optics,resonant dispersive waves
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Numerical and Experimental Study on the IR Femtosecond Laser and Phase Mask-Based Grating Inscription in Photonic Crystal Fibers
摘要： Femtosecond pulse laser sources enable the fabrication of fiber Bragg gratings (FBGs) in non-photosensitive fibers, allow for through coating grating inscription when working at infrared (IR) wavelengths and can provide for high temperature stable gratings. Target applications for such gratings include, but are not limited to, optical communications, fiber lasers and fiber sensing. When dealing with such grating inscription method in photonic crystal fibers (PCF) however, the presence of air holes in the fiber cladding impedes the delivery of the femtosecond laser pulse energy to the fiber core, which in its turn significantly affects the index change through non-linear absorption processes in the fiber core [1]. Our research focuses on this issue in view of understanding how the grating writing laser pulses interact with the PCF’s holey structure and of enabling more efficient femtosecond laser-based inscription of FBGs in PCFs. Here we report on the inscription of FBGs in a hexagonal lattice PCF using a femtosecond pulse laser operating at 1030 nm with a phase mask and a short focal length cylindrical lens (f=10 mm) that focuses light to the fiber core [2]. We first looked into the influence of the alignment on laser beam focusing in the cross-section of the PCF by comparing the focusing characteristics to those in standard step-index single mode fiber. As a figure of merit, we used the transverse coupling efficiency (TCE), which is defined as the ratio of the integrated core field intensities simulated (using Lumerical FDTD Solutions?) in the presence and absence of holey cladding. Fig. 1b shows how the TCE changes as the fiber is translated along the X and Y axes in the cross-sectional plane. X=0 and Y=0 corresponds to focused to the center of the core, and negative Y indicates translation of the fiber away from the lens (see Fig. 1a). For a step-index fiber we observe a typically elongated region in which we find optimal coupling with TCE=1 (no air holes) for a beam waist of 2.34 μm and a depth of focus of 15.7 μm. Fig. 1c shows an alignment map for a hexagonal lattice PCF (with structure shown in the inset of Fig. 1d), when light is incident along the ΓK axis of the hexagon. We can identify three distinct regions with a TCE around 0.6. Those appear when the fiber is shifted by around 15 μm and 30 μm further from the lens. This offset indicates that optimal coupling of the grating writing beam to the PCF core requires focusing to the edge of the holey cladding or closer to the silica cladding region of the fiber, rather than to the core center. Fig. 1 a) Fiber translational axes and translation dependence of the transverse coupling efficiency (TCE) for b) step-index fiber and c) PCF. d) Spectra of the IR femtosecond pulse inscribed FBG in the PCF (SEM image in the inset). We then inscribed FBGs in the above mentioned hexagonal lattice PCF with a commercial Yb:KGW ultrafast regenerative amplifier system Pharos 6W (Light Conversion) at 1030 nm and 190 fs duration pulses at a repetition rate of 100 Hz. We used high accuracy alignment stages to find the best coupling position by monitoring the luminescence (around 420 nm) from the Ge-doped core. The reflection and transmission spectra of the inscribed FBG are shown in Fig. 1c. We achieved an almost 4 dB strong FBG in around 4 seconds using a laser power of 450 mW. To the best of our knowledge it is the first time that the difference between regular step-index fibers and PCFs in best focusing conditions for IR femtosecond laser-based FBG writing is studied and that such a FBG is realized in a PCF using a 1030 nm source and a phase mask technique with a short focal length cylindrical lens.
关键词： phase mask,photonic crystal fibers,Femtosecond pulse laser,fiber Bragg gratings,transverse coupling efficiency
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Coupling Distant Quantum Dots using a Photonic Crystal Fano Structure
摘要： Building a quantum computer by taking the advantage of quantum entanglement can lead to a significant increase in our ability to solve certain types of problems. Quantum computer has run on various forms in which photon has been recognized as a highly desirable one due to the robustness of photonic states against decoherence. In particular, it is promising to use a semiconductor on-chip nanophotonic system where photons can be manipulated via combinations of cavities and waveguides (WGs) [1] because of its multi-functionalities, robustness and scalability towards highly integrated chips. Photonic nanocavities combined with semiconductor quantum dots (QDs) constitute one of the best candidates [2]. To achieve QD-QD coupling, it is usually proposed to place the nanocavities, embedded with QDs, in close proximity with their physical distance on the order of a few wavelengths because the cavity mode is usually tightly confined in space, resulting in limited penetration depth of the evanescent fields. However, going beyond short-distant coupling to long-distant coupling is essential because of the requirement of producing and maintaining entanglement between spatially separated qubits on-chip, both for measurement purposes and to permit individual control of separated qubits. Here a photonic crystal (PhC) nanocavity coupled WG structure is proposed where two nanocavities, separated by ~20 wavelengths, with each incorporating a semiconductor QD, are side coupled with an open bus WG. If the structure is properly designed, light originally leaking out through the WG will experience destructive interferences at the WG outputs due to the Fano interference effect [3, 4], leading to a high-Q optical mode that is confined only between the two cavities, cf. Fig. 1(a). Such a configuration can promote a strong coupling between the two cavities without causing mode doubling which is the usual case in coupled cavity systems, even if the two cavities are well separated in space, thus facilitating distant QD-QD interactions. A Green function based approach [5, 6] is used to investigate the quantum dynamics of the system so the loss in the open system is taken into account automatically. Numerical simulations show that QD 2 can be well excited even if only QD 1 is driven, cf. Fig. 1(b). In addition, a sound concurrence, a measure of entanglement between the two QDs, and a Mollow triplet in the QD emission can be observed, reflecting a well coupling between the two QDs, thanks to their strong interactions with the optical Fano mode. Future work aims for structure optimizations as well as experimental demonstration of distant QD-QD entanglement, combined with site-controlled semiconductor QDs [7].
关键词： photonic crystal,quantum entanglement,quantum computer,quantum dots,Fano interference
更新于2025-09-12 10:27:22
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Holographic fabrication of octagon graded photonic supercrystal and potential applications in topological photonics
摘要： Novel optical properties in graded photonic super-crystals can be further explored if new types of graded photonic super-crystals are fabricated. In this paper, we report holographic fabrication of graded photonic super-crystal with eight graded lattice clusters surrounding the central non-gradient lattices through pixel-by-pixel light modulator. The phase engineering in a spatial prospect of applications of octagon graded photonic super-crystal in topological photonics is discussed through photonic band gap engineering and coupled ring resonators.
关键词： 2D photonic crystal,photonic band structure,holographic fabrication,graded photonic super-crystal
更新于2025-09-11 14:15:04
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Sensitive Temperature Sensors based on High Birefringence Liquid-Filled Photonic Crystal Fibers
摘要： We propose a new design of a highly birefringent photonic crystal fiber (HBPCF) via infiltration of two holes adjacent to the core of the fiber with two different liquids. As the refractive index of liquids is sensitive to temperature variations, the proposed HBPCF can be used in a Sagnac interferometer as a highly sensitive temperature sensor. The proposed HBPCF can show birefringence of 4 × 10-4 and birefringence sensitivity of 25% for a 5oc temperature variation around 25oc which corresponds to a sensitivity of around 10 nm/oc.
关键词： liquid filled photonic crystal fiber,fiber optic sensor,temperature sensor photonic crystal fiber
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Dually-Modulated Photonic-Crystal Lasers for Beam Scanning
摘要： Mechanical-free, high-power, high-beam quality two-dimensional beam scanning is strongly required for LiDAR systems for autonomous driving. Here, we propose and demonstrate a new, dually-modulated photonic crystal laser, with which we successfully emit a high-quality laser beam with watt-class power in any desired direction.
关键词： PCSEL (Photonic-Crystal Surface-Emitting Laser),Photonic Crystal,2D Beam Scanning
更新于2025-09-11 14:15:04
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Simulations of LED Patterned with IP-DIP Woodpile Structure
摘要： In this paper, we present simulations of three-dimensional (3D) photonic crystal structure (PhC) in IP-Dip polymer. We investigated woodpile structure and LED patterned by woodpile structure by various simulation methods. Structure was designed by the computer aided design (CAD) and optical properties were simulated by finite-difference time-domain (FDTD) and rigorous coupled-wave analyses (RCWA) simulation methods. We are focused on diffraction of optical radiation by woodpile structure and possibility of influencing extraction ratio and radiation patterns of LED with patterned woodpile structure. There is improving a significant percentage of transmittance of the radiation. It results in the influence of the radiation from the LED and it has positive impact on the LED parameters.
关键词： photonic crystal,simulations,3D woodpile structure,light extraction,photonic band gap,radiation pattern
更新于2025-09-11 14:15:04