一维多孔硅光子晶体反射特性及制作的理论研究

在一维光子晶体光学传输特性理论的基础上,运用传输矩阵法推导了一维多孔硅光子晶体的反射特性,并对其反射特性与结构参数的关系进行了分析。给出了采用脉冲电化学阳极腐蚀法制备一维多孔硅光子晶体的制作模型。利用计算机数值模拟的方法给出了各种一维多孔硅光子晶体的典型反射谱。为多孔硅光子晶体的实际应用奠定了理论基础。     

Two modes of laser lithography fabrication of three-dimensional submicrometer structures

The modes of laser lithography fabrication of three-dimensional submicrometer structures have been studied. The method is based on the effect of threshold two-photon polymerization of a photosensitive material at the laser beam focus. To determine the lithograph workspace in the coordinates “laser power-speed of the sample displacement with respect to the laser focus,” a series of photonic crystals with the woodpile structure is prepared. Two methods for fabricating three-dimensional structures, i.e., raster scanning and vector graphics (or the vector method) are analyzed in detail. The advantages of the vector method for fabricating periodic structures are demonstrated using crystals of inverted yablonovite as an example. The prepared samples are studied by scanning electron microscopy.     

Modeling of the optical properties of porous silicon photonic crystals in the visible spectral range

Optical devices based on photonic crystals are of great interest because they can be efficiently used in laser physics and biosensing. Photonic crystals allow one to control the propagation of electromagnetic waves and to change the emission characteristics of luminophores embedded into photonic structures. One of the most interesting materials for developing one-dimensional photonic crystals is porous silicon. However, an important problem in application of this material is the control of the refractive index of layers by changing their porosity, as well as the refractive index dispersion. In addition, it is important to have the possibility of modeling the optical properties of structures to choose precisely select the fabrication parameters and produce one-dimensional photonic crystals with prescribed properties. In order to solve these problems, we used a mathematical model based on the transfer matrix method, using the Bruggeman model, and on the dispersion of silicon refractive index. We fabricated microcavities by electrochemical etching of silicon, with parameters determined by the proposed model, and measured their reflection spectra. The calculated results showed good agreement with experimental data. The model proposed allowed us to achieve a microcavity Q-factor of 160 in the visible region.     

激光全息光刻技术在微纳光子结构制备中的应用进展

微纳光子结构研究随着光子学、半导体物理学及微加工技术的发展而逐渐蓬勃开展,并在其结构、理论、制备技术等方面取得了系列进展。受限于目前的微加工技术水平,要成功制备大尺度、高质量的光子材料仍然存在着一定挑战。激光全息光刻技术作为一种简便快捷的微结构制作技术已经发展成为一种经济快速制作大面积微纳超材料及光子晶体模板的重要手段。介绍了激光全息光刻技术的原理,详细阐述了该技术在制作三维面心立方、木堆积结构、金刚石结构光子晶体以及光学周期类准晶、手性超材料、周期性缺陷结构等微纳光子结构中的应用研究进展。激光全息光刻技术成功制作微纳光子结构为光子材料在更多领域的广泛应用提供了基础和方法。     

The three-dimensional photonic crystals coated by gold nanoparticles

We report on the fabrication of metallodielectric photonic crystals by means of interference lithography and subsequent coating by gold nanoparticles. The grating is realized in a SU-8 photoresist using a He-Cd laser of wavelength 442 nm. The use of the wavelength found within the photoresist low absorption band enables fabricating structures that are uniform in depth. Parameters of the photoresist exposure and development for obtaining a porous structure corresponding to an orthorhombic lattice are determined. Coating of photonic crystals by gold nanoparticles is realized by reduction of chloroauric acid by a number of reductants in a water solution. This research shows that the combination of interference lithography and chemical coating by metal is attractive for the fabrication of metallodielectric three-dimensionally periodic microstructures.     

二维光子晶体的软平板印刷技术制作研究

分析了软平板印刷技术制作二维光子晶体的特点和方法.利用绝缘PDMS模板,采用软平板印刷技术制造了三角晶系结构的二维聚合物光子晶体,采用同样的技术成功制成尺寸为150~500 nm,纵横比达1.25的高密度二维光子晶体.与其他制作技术相比,平板印刷技术具有大尺寸和易于制作的优点.结果表明,制作获得的微结构有很高的保真度.     

Silicon-based two-dimensional photonic crystal waveguides

A review of the properties of silicon-based two-dimensional (2D) photonic crystals is given, essentially infinite 2D photonic crystals made from macroporous silicon and photonic crystal slabs based on silicon-on-insulator basis. We discuss the bulk photonic crystal properties with particular attention to the light cone and its impact on the band structure. The application for wave guiding is discussed for both material systems, and compared to classical waveguides based on index-guiding. Losses of resonant waveguide modes above the light line are discussed in detail.     

Photonic band gaps based on tetragonal lattices of slanted pores

We describe broad new classes of three-dimensional (3D) structures which, when made of silicon, exhibit robust 3D photonic band gaps of up to 25% of the gap center frequency. The proposed photonic crystals are readily amenable to very high precision microfabrication using established techniques such as x-ray lithography and template inversion. Each architecture consists of a set of oriented cylindrical pores emanating from a two-dimensional (2D) square lattice mask with a two-point basis. Large bandwidth, microcircuits for light may be incorporated within the resulting photonic band gaps using an intercalated 2D photonic crystal layer.     

Optical properties of one-dimensional photonic crystals obtained by micromatchining silicon (a review)

The theoretical and experimental investigations of photonic band gaps in one-dimensional photonic crystals created by micromatchining silicon, which have been performed by the author as part of his doctoral dissertation, are presented. The most important result of the work is the development of a method of modeling photonic crystals based on photonic band gap maps plotted in structure–property coordinates, which can be used with any optical materials and in any region of electromagnetic radiation, and also for nonperiodic structures. This method made it possible to realize the targeted control of the optical contrast of photonic crystals and to predict the optical properties of optical heterostructures and three-component and composite photonic crystals. The theoretical findings were experimentally implemented using methods of micromatchining silicon, which can be incorporated into modern technological lines for the production of microchips. In the IR spectra of a designed and a fabricated optical heterostructure (a composite photonic crystal), extended bands with high reflectivities were obtained. In a Si-based three-component photonic crystal, broad transmission bands and photonic band gaps in the middle IR region have been predicted and experimentally demonstrated for the first time. Si–liquid crystal periodic structures with electric-field tunable photonic band-gap edges have been investigated. The one-dimensional photonic crystals developed based on micromatchining silicon can serve as a basis for creating components of optical processors, as well as highly sensitive chemical and biological sensors in a wide region of the IR spectrum (from 1 to 20 μm) for lab-on-a-chip applications.     

Study on the thermal isolation properties of porous silicon photonic crystal

The thermal isolation properties of porous silicon photonic crystal structures have been designed and discussed theoretically. Excellent thermal isolation properties can be obtained on such a porous silicon photonic crystal, even better than that of porous silicon with high porosity. Due to the excellent thermal isolation properties of the porous silicon photonic crystal structures, they can be used as the thermal isolation substrates in infrared detectors     

Nanostructured one-and three-dimensional magnetophotonic crystals based on porous silicon and artificial opals

Nanostructured one-and three-dimensional magnetophotonic crystals are produced by infiltration of yttrium-iron garnet with bismuth into photonic crystals based on porous silicon and artificial opals. The magnetic properties of the resulting structures are studied by generation of the magnetically induced second harmonics. The magnetic contrast of the second harmonics intensity in the spectral region of the photonic gap edge of the photonic crystal is 10–15%.     

Synthesis and characterization of porous silicon layers for 1D photonic crystal application

In this paper, we studied the optical and physical properties of electrochemically prepared porous silicon layers. The atomic force microscopy analysis showed that the etching depth, pore diameter and surface roughness increase as the etching time increased from 30 to 50 mA/cm². By tuning two current densities J₁ = 50 mA/cm² and J₂ = 30 mA/cm², two samples of 1D porous silicon photonic crystals were fabricated. The layered structure of 1D photonic crystals has been confirmed by scanning electron microscopy measurement which showed white and black strips of two distinct refractive index layers. Finally, the measured reflectance spectra of 1D porous silicon photonic crystals were compared with simulated results.     

Two-dimensional materials-decorated microfiber devices for pulse generation and shaping in fiber lasers

Two-dimensional(2D) materials have been regarded as a promising nonlinear optical medium for fabricating versatile optical and optoelectronic devices. Among the various photonic applications, the employment of 2D materials as nonlinear optical devices such as saturable absorbers for ultrashort pulse generation and shaping in ultrafast lasers is one of the most striking aspects in recent years. In this paper, we review the recent progress of 2D materials based pulse generation and soliton shaping in ultrafast fiber lasers, and particularly in the context of 2D materials-decorated microfiber photonic devices. The fabrication of 2D materials-decorated microfiber photonic devices, high performance mode-locked pulse generation, and the nonlinear soliton dynamics based on pulse shaping method are discussed. Finally, the challenges and the perspective of the 2D materials-based photonic devices as well as their applications are also discussed.     

New approaches for the fabrication of photonic structures of nonlinear optical materials

We revisited two different strategies to fabricate 1D photonic crystals of nonlinear optical dielectric materials based on ultrafast laser ablation of the surface of an RbTiOPO₄ crystal, and selective etching of ferroelectric domains of the surface of a periodically poled LiNbO₄ crystal. We evaluated their behaviour as Bragg diffraction gratings. We also presented the recent advances we developed in a new procedure of fabrication of 2D and 3D photonic crystals of KTiOPO₄ (KTP) grown on the surface of a KTP substrate by liquid phase epitaxial means within the pores of a silicon macroporous template. Optical, structural, morphological, and compositional characterization for the photonic crystals produced through this technique are presented.     

Simulation and fabrication study of porous silicon photonic crystal

The present work reports design and fabrication of porous silicon based one-dimensional (1D) photonic crystal. Distributed Bragg reflector (DBR) is a 1D photonic crystal composed of multilayer stack of high and low refractive index layers. Design of porous silicon DBR is a complex one and requires appropriate control in optical parameters of its constituent layers. In order to design DBR, two porous silicon single layer samples were fabricated using current density of 10 and 50 mA/cm². Optical characterization of single layer samples showed series of interference fringes. Reflective interferometric Fourier transform spectroscopy (RIFTS) method was employed to determine optical constants of porous silicon single layers. DBR simulation was carried out based on transfer matrix method. DBR was then fabricated using optical parameters obtained from RIFTS method. Reflection bandwidth of prepared DBR was found to be 216 nm, which is comparable to the simulated value of 203 nm.     

A new fabrication technique for photonic crystals: Nanolithography combined with alternating-layer deposition

We propose two photonic crystal structures that can be created by combining nanolithography with alternating-layer deposition. Photonic band calculations suggest that a drilled alternating-layer photonic crystal combining two-dimensional (2D) alternating multilayers and an array of vertically drilled holes may achieve a full photonic bandgap. In addition, a 3D/2D/3D cross-dimensional photonic crystal, which sandwiches a 2D photonic crystal slab between three-dimensional (3D) alternating-layer photonic crystals, should provide better vertical confinement of light than a conventional index guiding slab. Fabrication techniques based on existing technologies (electron beam lithography, bias sputtering, and low-pressure ECR etching) require very few process steps. Our preliminary fabrication suggests that, by refining these technologies, we will be able to realize photonic crystals.     

硅基二维光子晶体耦合器理论研究

光子晶体是一种具有光子带隙的新型人工材料,利用其具有控制和限制光子运动的特性可以制成新颖的光学器件。利用硅基二维光子晶体,提出了一种4端口耦合器。采用时域有限差分法作为研究工具,TM模作为研究对象,从理论上分析了这种器件的特性。在不同的耦合长度下研究光在输出端的功率透射率。结果表明选择适当的耦合长度可以使光在器件中呈现不同的状态。进一步研究表明,通过改变器件内部介质柱的半径,可以改变光在输出端的输出功率。从而证实了这种器件不仅具有波长选择性,而且具有潜在的可调节性,这些特性使得这种器件在全光开关的应用上具有潜在的优势。     

Thermal emission properties of 2D and 3D silicon photonic crystals

We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals with and without substrate heated resistively as well as passively with an aluminium hotplate. The out-of-plane and in-plane emission properties were recorded and compared to numerical simulation. It turned out that for the in-plane 2D photonic crystal and out-of-plane 3D photonic crystal emission a photonic stop gap effect is visible. For the out-of-plane 2D photonic crystal emission, no photonic bandgap effect is observable but instead strong silicon oxide emission from native oxide inside the pores of silicon are observable. A model for the modified thermal emission is presented.     

Direct optical fabrication of three-dimensional photonic crystals in a high refractive index LiNbO3 crystal

Direct optical fabrication of 3D photonic crystals in a high refractive index LiNbO3 crystal by using the femtosecond laser-induced microexplosion method is investigated. The focal distortion, caused by the refractive index mismatch-induced spherical aberration, can be significantly reduced by using a so-called threshold fabrication method. As a result, 3D fcc photonic crystals are fabricated by stacking quasi-spherical voids layer by layer. Photonic stopgaps with suppression rates of up to 30% in the transmission spectra are observed. The angle dependence of the stopgaps is also revealed.     

Simulation of surface-modified porous silicon photonic crystals for biosensing applications

In this work realistic biosensing structures based on the integration of porous silicon photonic crystals with polymer coating technology are presented. Microcavities and rugate filters are chosen as the photonic crystal configuration. The deposition of a polymer layer on the pore walls of these structures is proposed to improve the selectivity and sensitivity of the sensing function. A complete effective refractive index model including the polymer layer, the target and external effects like silicon oxidation has been developed in order to accurately simulate the structures. It is expected that the proposed structures could be used as low cost, highly integrated and highly sensitive biological sensors.