Super Bound States in the Continuum on a Photonic Flatband: Concept, Experimental Realization, and Optical Trapping Demonstration.

In this Letter, we theoretically propose and experimentally demonstrate the formation of a super bound state in a continuum (BIC) on a photonic crystal flat band. This unique state simultaneously exhibits an enhanced quality factor and near-zero group velocity across an extended region of the Brillouin zone. It is achieved at the topological transition when a symmetry-protected BIC pinned at k=0 merges with two Friedrich-Wintgen quasi-BICs, which arise from the destructive interference between lossy photonic modes of opposite symmetries. As a proof of concept, we employ the ultraflat super BIC to demonstrate three-dimensional optical trapping of individual particles. Our findings present a novel approach to engineering both the real and imaginary components of photonic states on a subwavelength scale for innovative optoelectronic devices.

Huge light-enhancement by coupling a Bowtie Nano-antenna's plasmonic resonance to a photonic crystal mode.

We numerically demonstrate a drastic enhancement of the light intensity in the vicinity of the gap of Bowtie Nano-antenna (BA) through its coupling with Photonic Crystal (PC) resonator. The resulting huge energy transfer toward the BA is based on the coupling between two optical resonators (BA and PC membrane) of strongly unbalanced quality factors. Thus, these two resonators are designed so that the PC is only slightly perturbed in term of resonance properties. The proposed hybrid dielectric-plasmonic structure may open new avenues in the generation of deeply subwavelength intense optical sources, with direct applications in various domains such as data storage, non-linear optics, optical trapping and manipulation, microscopy, etc.

Light funneling from a photonic crystal laser cavity to a nano-antenna: overcoming the diffraction limit in optical energy transfer down to the nanoscale.

We show that the near-field coupling between a photonic crystal microlaser and a nano-antenna can enable hybrid photonic systems that are both physically compact (free from bulky optics) and efficient at transferring optical energy into the nano-antenna. Up to 19% of the laser power from a micron-scale photonic crystal laser cavity is experimentally transferred to a bowtie aperture nano-antenna (BNA) whose area is 400-fold smaller than the overall emission area of the microlaser. Instead of a direct deposition of the nano-antenna onto the photonic crystal, it is fabricated at the apex of a fiber tip to be accurately placed in the microlaser near-field. Such light funneling within a hybrid structure provides a path for overcoming the diffraction limit in optical energy transfer to the nanoscale and should thus open promising avenues in the nanoscale enhancement and confinement of light in compact architectures, impacting applications such as biosensing, optical trapping, local heating, spectroscopy, and nanoimaging.

Strong confinement of light in low index materials: the Photon Cage.

New photonic microstructures are proposed for an efficient light trapping in low index media. Cylindrical hollow cavities formed by bending a photonic crystal membrane are designed. Using numerical simulations, strong confinement of photons is demonstrated for very open resonators. The resulting strong light matter interaction can be exploited in optical devices comprising an active material embedded in a low index matrix like polymer or even gaz.

Dual-wavelength micro-resonator combining photonic crystal membrane and Fabry-Perot cavity.

We propose a novel system of dual-wavelength micro-cavity based on the coupling between a photonic crystal membrane (PCM); operating at the Γ- point of the Brillouin zone, with a Fabry-Perot vertical cavity (FP). The optical coupling, which can be adjusted by the overlap between both optical modes, leads to the generation of two hybrid modes separated by a frequency difference which can be tuned using micro-opto-electromechanical structures. The proposed dual-wavelength micro-cavity is attractive for application where dual-mode behaviour is desirable as dual-lasing, frequency conversion. An analytical model, numerical (FDTD) and transfer matrix method investigations are presented.

3D light harnessing based on coupling engineering between 1D-2D Photonic Crystal membranes and metallic nano-antenna.

A new approach is proposed for the optimum addressing of a metallic nano-antenna (NA) with a free space optical beam. This approach relies on the use of an intermediate resonator structure that provides the appropriate modal conversion of the incoming beam. More precisely, the intermediate resonator consists in a Photonic Crystal (PC) membrane resonant structure that takes benefit of surface addressable slow Bloch modes. First, a phenomenological approach including a deep physical understanding of the NA-PC coupling and its optimization is presented. In a second step, the main features of this analysis are confirmed by numerical simulations (FDTD).

A simple perturbative analysis for fast design of an electrically pumped micro-disk laser.

A perturbative analysis is proposed to estimate optical losses for electrically pumped micro-disk lasers. The optical field interaction with the electrical contacts and the optimization of their implementation is investigated. Our model shows a good agreement with 3D Finite Difference Time Domain (FDTD) computation and can be used for designing contacts for thin micro-disks, with a considerably reduced calculation time. We also demonstrate that losses induced by the contacts can be exploited to select the optical mode of a micro-laser.

Room temperature low-threshold InAs/InP quantum dot single mode photonic crystal microlasers at 1.5 microm using cavity-confined slow light.

We have designed, fabricated, and characterized an InP photonic crystal slab structure that supports a cavity-confined slow-light mode, i.e. a bandgap-confined valence band-edge mode. Three dimensional finite difference in time domain calculations predict that this type of structure can support electromagnetic modes with large quality factors and small mode volumes. Moreover these modes are robust with respect to fabrication imperfections. In this paper, we demonstrate room-temperature laser operation at 1.5 mum of a cavity-confined slow-light mode under pulsed excitation. The gain medium is a single layer of InAs/InP quantum dots. An effective peak pump power threshold of 80 microW is reported.

Surface emitting microlaser based on 2D photonic crystal rod lattices.

2D photonic crystal (2D PC) structures consisting in a square lattice of Indium Phosphide (InP) microrods bonded on a Silicon/Silica Bragg mirror are experimentally investigated. We focus on slow Bloch modes above the light line, especially at the Gamma-point where a vertical emission can be obtained. Stimulated emission around 1.5 microm is demonstrated in such structures, at room temperature, for the first time. In addition the achieved threshold power lies within the range reported for surface emitting devices based on conventional lattices of holes. It is shown that the laser mode is laterally confined by a carrier induced refractive index change, under pulsed excitation. It is also demonstrated that this type of 2D PC is well suited for sensors integrated in microfluidic systems.

Absorption enhancement using photonic crystals for silicon thin film solar cells.

We propose a design that increases significantly the absorption of a thin layer of absorbing material such as amorphous silicon. This is achieved by patterning a one-dimensional photonic crystal (1DPC) in this layer. Indeed, by coupling the incident light into slow Bloch modes of the 1DPC, we can control the photon lifetime and then, enhance the absorption integrated over the whole solar spectrum. Optimal parameters of the 1DPC maximize the integrated absorption in the wavelength range of interest, up to 45% in both S and P polarization states instead of 33% for the unpatterned, 100 nm thick amorphous silicon layer. Moreover, the absorption is tolerant with respect to fabrication errors, and remains relatively stable if the angle of incidence is changed.

Two-dimensional surface emitting photonic crystal laser with hybrid triangular-graphite structure.

We present laser emission of a compact surface-emitting micro laser, optical pumped and operating at 1.5 microm at room temperature. A two-dimensional photonic crystal lattice conformed in a hybrid triangular-graphite configuration is designed for vertical emission. The structures have been fabricated in an InP slab, including four InAsP quantum wells as active layer, on the top of a Si substrate SiO(2) wafer bonded. Laser emission with thresholds around 70 microW and quality factors (Qs) up to 12000 have been measured. The Bloch mode selected for the emission keeps a high Q (>or= 2 x 10(5)) around the Gamma point for a wide range of in-plane values k(||)

Microlasers based on effective index confined slow light modes in photonic crystal waveguides.

We present the design, theory and experimental implementation of a low modal volume microlaser based on a line-defect 2D-photonic crystal waveguide. The lateral confinement of low-group velocity modes is controlled by the post-processing of 1 to 3microm wide PMMA strips on top of two dimensional photonic crystal waveguides. Modal volume around 1.3 (lambda/n)(3) can be achieved using this scheme. We use this concept to fabricate microlaser devices from an InP-based heterostructure including InAs(0.65)P(0.35) quantum wells emitting around 1550nm and bonded onto a fused silica wafer. We observe stable, room-temperature laser operation with an effective lasing threshold around 0.5mW.

Optofluidic integration of a photonic crystal nanolaser.

We demonstrate a new type of photonic crystal nanolaser incorporated into a microfluidic chip, which is fabricated by multilayer soft lithography. Experimentally, room-temperature continuous-wave lasing operation was achieved by integrating a photonic crystal nanocavity with a microfluidic unit, in which the flow medium both enhances the rate of heat removal and modulates the refractive index contrast. Furthermore, using the proposed system, dynamic modulation of the resonance wavelength and far-field radiation pattern can be achieved by introducing a bottom reflector across which various fluids with different refractive indices are forced to flow. In particular, by maintaining a gap between the reflector and the cavity equal to the emission wavelength, highly efficient unidirectional emission can be obtained. The proposed nanolasers are ideal platforms for highfidelity biological and chemical detection tools in micro-total-analytical or lab-on-a-chip systems.

Effect of implementation of a Bragg reflector in the photonic band structure of the Suzuki-phase photonic crystal lattice.

We investigate the change of the photonic band structure of the Suzuki-phase photonic crystal lattice when the horizontal mirror symmetry is broken by an underlying Bragg reflector. The structure consists of an InP photonic crystal slab including four InAsP quantum wells, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Angle- and polarization-resolved photoluminescence spectroscopy has been used for measuring the photonic band structure and for investigating the coupling to a polarized plane wave in the far field. A drastic change in the k-space photonic dispersion between the structure with and without Bragg reflector is measured. An important enhancement on the photoluminescence emission up to seven times has been obtained for a nearly flat photonic band, which is characteristic of the Suzuki-phase lattice.

Theoretical and experimental study of the Suzuki-phase photonic crystal lattice by angle-resolved photoluminescence spectroscopy.

A complete theoretical and experimental analysis of the photonic band structure for the Suzuki-phase lattice is presented. The band diagrams were calculated by two-dimensional plane wave expansion and three-dimensional guided-mode expansion methods. Angle resolved photoluminescence spectroscopy has been used to measure the emission of the photonic crystal structure realized in active InAsP/InP slabs. Photonic bands with a very low group velocity along an entire direction of the reciprocal lattice have been measured, which may have important applications on future photonic devices. The experimentally determined dispersion is in very good agreement with the calculated photonic bands. The presence of defect modes produced by microcavities in the Suzuki-phase lattice has also been established.

Room-temperature InAs/InP Quantum Dots laser operation based on heterogeneous "2.5 D" Photonic Crystal.

The authors report on the design, fabrication and operation of heterogeneous and compact "2.5 D" Photonic Crystal microlaser with a single plane of InAs quantum dots as gain medium. The high quality factor photonic structures are tailored for vertical emission. The devices consist of a top two-dimensional InP Photonic Crystal Slab, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Despite the fact that no more than about 5% of the quantum dots distribution effectively contribute to the modal gain, room-temperature lasing operation, around 1.5 microm, was achieved by photopumping. A low effective threshold, on the order of 350 microW, and a spontaneous emission factor, over 0.13, could be deduced from experiments.

Directional channel-drop filter based on a slow Bloch mode photonic crystal waveguide section.

A two-dimensional photonic crystal channel-drop filter is proposed. This device has two high group velocity waveguides that are selectively coupled by a single, low group velocity intermediate waveguide section. It exhibits computed quality factors as high as 1300, and directional dropping efficiencies as high as 90%.

Coupling analysis of heterogeneous integrated InP based photonic crystal triangular lattice band-edge lasers and silicon waveguides.

In recent years, many groups have envisioned the possibility of integrating optical and electronic devices in a single chip. In this paper, we study the integration of a photonic crystal laser fabricated in InP with a silicon passive waveguide. The coupling of energy between a 2D photonic crystal (PhC) triangular lattice band-edge laser and waveguide positioned underneath is analyzed in this paper. We show that a 40% coupling could be achieved provided the distance between the laser and the waveguide is carefully adjusted. A general description of the fabrication process used to realize these devices is also included in this paper.

Analysis of hybrid photonic crystal vertical cavity surface emitting lasers.

Vertical resonators with a top mirror constituted of 1D photonic crystal membrane on top of a Bragg stack are investigated in this paper. These structures allow the fabrication of compact vertical-cavity surfaceemitting lasers, which can be designed, in addition, for in-plane emission. With this hybrid approach, fabrication problems related to both classical VCSEL and Photonic Crystal lasers may be significantly relaxed, given that a full Bragg stack is replaced by a single photonic crystal membrane and that the Photonic Crystal is not formed in the active gain layer.