• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 115
  • 31
  • 21
  • 20
  • 19
  • 18
  • 4
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 270
  • 270
  • 68
  • 63
  • 55
  • 41
  • 35
  • 29
  • 26
  • 25
  • 24
  • 23
  • 22
  • 21
  • 20
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Fabrication of Quantum Dots Lasers of two dimensional Photonic Crystal Microcavity Structures

Huang, Shr-Chiuan 28 July 2010 (has links)
In the thesis, we fabricated the quantum dots lasers of 2D photonic crystal microcavity structures by E-beam lithography. The Al0.5Ga0.5As sacrificing layer beneath the Dwells structure is used for the purpose of suspending the active layer by air. Therefore, it has a high refractive index contrast in vertical direction to confine energy. Finally, we could fabricate a low threshold current photonic crystal laser. We can judge the epitaxy quality by the Microdisk (MD) process before the photonic crystal device process. For the 2D photonic crystal microcavity, we design different kinds of window to support the photonic crystal membrane cavity. We use dry and wet etching technique and metal mask to fabricate MD and photonic crystal membrane cavity. We use £g-PL to measure MD cavity resonant mode for the device of diameter 3£gm at room temperature. In addition, we design three kinds of defects (L3, H2, H3) of photonic crystal membrane structures using the sample C488. We measure resonant mode with H3 structure. The H3 structure measured resonant wavelength 1.26£gm, with Q =503.
2

Reconfigurable Photonic Crystal Cavities

Smith, Cameron January 2009 (has links)
Doctor of Philosophy (PhD) / Photonic crystals are optical structures that contain a periodic modulation of their refractive index, allowing them to control light in recent years of an unprecedented capacity. Photonic crystals may take on a variety of configurations, in particular the photonic crystal cavity, which may “hold” light in small volumes comparable to the light’s wavelength. This capability to spatially confine light opens up countless possibilities to explore for research in telecommunications, quantum electrodynamics experiments and high-resolution sensor applications. However, the vast functionality potentially made available by photonic crystal cavities is limited due to the difficulty in redefining photonic crystal components once they are formed in their (typically) solid material. The work presented in this thesis investigates several approaches to overcome this issue by reconfiguring photonic crystal cavities.
3

Applications of E-Beam Lithography to the Fabrication of Photonic Crystal Microcavity and DBR Laser

Pai, Chun-Cheng 30 July 2007 (has links)
In this thesis, we use E-Beam lithography to finish the process of DBR laser, 2D Photonic crystal, and Metallic nanoelectrodes. We use the new E-Beam system to define array patterns. By this test, we obtain the minimum linewidth of 50nm, and the maximum working range is 250£gm*250£gm. We fabricated the 2D photonic crystal microcavity and DBR laser on the InGaAs/InAlGaAs which was grown by molecular beam epitaxy (MBE) on InP substrate. For the DBR laser, the length of Multi-mode Interference (MMI) was 90£gm to satisfied the emission wavelength and optical modes. We apply a coupled DBR reflector on both sides of MMI. The mirror width was 361nm and the air gap was 388nm. For the 2D photonic crystal (2D PhC) microcavity, a triangular array of air columns was adopted. The lattice constant and air columns radius are 1137nm and 456nm, respectively. The TE-mode photonic band gap of this structure is corresponding to wavelength range in 1517.01 nm~1617.81 nm. We leave a single defect in the 2D PhC to form 2D PhC microcavity and the corresponding defect modes are 1546.32nm and 1547.74nm. The Micro-PL measurement shows that a defect mode at 1547nm (a/£f=0.74), a surface state at 1351nm (a/£f=0.85), and a standing wave at 1480nm (a/£f=0.78). The maximum Q value is about 400 for the defect mode.
4

Experimental Verification of a Three Dimensional Photonic Crystal Bandgap

Jamalapur, Sri Abhishek 25 July 2012 (has links)
Photonic crystals (PC) are periodic structures that dictate the behavior of electromagnetic radiation and can be one-dimensional, two-dimensional or three-dimensional (3D). A 3DPC was modeled and fabricated based on a three-layer design resulting in a face centered cubic structure. Different simulation methods were used to show the existence of a complete 3D bandgap, and were verified experimentally by obtaining transmission measurements in several directions. A prototype of the structure was fabricated using ECCOSTOCK HiK high dielectric sheets (dielectric of 12) and machined using a computer and numerical controlled mill. Experiments to test this structure were performed in an anechoic chamber making use of a network analyzer, a pair of horn antennas, collimating lenses, and a track for alignment. Free-space Thru-Reflect-Line measurements were taken between 10GHz and 15GHz to obtain the transmission through the prototype. Finally, a defect layer was added to the structure at different locations and localized modes observed.
5

Experimental Verification of a Three Dimensional Photonic Crystal Bandgap

Jamalapur, Sri Abhishek 25 July 2012 (has links)
Photonic crystals (PC) are periodic structures that dictate the behavior of electromagnetic radiation and can be one-dimensional, two-dimensional or three-dimensional (3D). A 3DPC was modeled and fabricated based on a three-layer design resulting in a face centered cubic structure. Different simulation methods were used to show the existence of a complete 3D bandgap, and were verified experimentally by obtaining transmission measurements in several directions. A prototype of the structure was fabricated using ECCOSTOCK HiK high dielectric sheets (dielectric of 12) and machined using a computer and numerical controlled mill. Experiments to test this structure were performed in an anechoic chamber making use of a network analyzer, a pair of horn antennas, collimating lenses, and a track for alignment. Free-space Thru-Reflect-Line measurements were taken between 10GHz and 15GHz to obtain the transmission through the prototype. Finally, a defect layer was added to the structure at different locations and localized modes observed.
6

The study of liquid crystal alignment in photonic crystal fiber

Chen, Ching-hsiang 02 July 2010 (has links)
This work presents a novel loss-reduced photonic liquid-crystal fiber (PLCF) using the non-contact photo-alignment method. The photo-excited and adsorbed azo dye on the capillary surface of a PLCF induces uniform and highly ordered orientation of the LC. The anchoring force of the photo-alignment effect is combined with that generated by surface boundary conditions of the photonic crystal fiber (PCF). Transmission loss resulting from LC scattering can be reduced from -2.8db/cm to -1.3db/cm within 10min. This photo-induced alignment yields a permanent boundary for the LC in the PCF that reduces scattering loss, and can be further modulated by electrical fields. The electrical tunable effect and fast dynamic response of the photo-aligned PLCF are also presented. This low-loss PLCF can be applied conveniently in various PLCF devices.
7

The Study and Fabrication of 2D amd Modified 1D Photonic Crystal Microcavity

Li, Ming-Chun 21 July 2005 (has links)
In this thesis, we fabricated the 2D photonic crystal and modified 1D photonic crystal microcavity on the InGaAs/GaAs substrate by E-beam lithography. The wafer are grown by molecular beam epitaxy (MBE) on GaAs substrate. The active layer consists of six InGaAs quantum wells at 1050nm emission wavelength. For the 1D photonic crystal microcavity (DBR laser),we changed the cavity shape and length to match the mode of light in the cavity. It can increase the reflectivity of the laser. In our simulations, we scanned different cavity length and found the corresponding data. We designed two and three pairs of DBRs formed on the edge of laser cavity, respectively. The cavity length is 121µm and the mirror width is 230nm and the air gap is 263nm. For the 2D photonic crystal (2DPC) microcavity, a triangular array of air columns was adopted. The lattice constant and air columns radius are 742nm and 304nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1026nm ~ 1089nm. We placed single defect in the 2DPCs to form 2DPC microcavities and the corresponding defect modes are 1051.58nm¡B1053.39nm and 1054.87nm. In addition, we reduced the air columns around the cavity and simulated the photonic bandgap and fabricated the devices by E-beam lithography and deep dry etching process.
8

The Study and Fabrication of 2D Photonic Crystal Microcavity and LC-DFB laser

Shiue, Chau-Wei 10 July 2006 (has links)
In this thesis, we fabricated the 2D photonic crystal microcavity and laterally coupled distributed feedback laser on InGaAs/InAlGaAs wafers by E-beam lithography. We also fabricated the 2D photonic crystal microcavity on the InGaAs/GaAs substrate at 980nm emission wavelength. The wafer are grown by molecular beam epitaxy (MBE). For the laterally coupled distributed feedback laser (LC-DFB laser) , we changed the grating shape and length to form proper grating, and it will make constructive diffraction and coupling. We design the mirror width is 180.55nm and the air gap is 541.65nm. For the 2D photonic crystal (2DPC) microcavity, a triangular array of air columns was adopted. The lattice constant and air columns radius are 1139nm and 456nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1522.72nm~1617.89nm. We placed single defect in the 2DPCs to form 2DPC microcavities and the corresponding defect modes are 1549.23nm and 1550.08nm. We have simulated the photonic bandgap and fabricated the devices by E-beam lithography and deep dry etching process. Also, we can use the same method to fabricate 980nm photonic crystal.
9

The Fabrication of Two Dimension Photonic Crystal and Positioning System

Hsu, Hung-hui 17 July 2008 (has links)
In this thesis, we use E-Beam lithography to finish the process of positioning system and 2D photonic crystal. We use the new E-Beam system to define some array patterns. By this test, we obtain the minimum linewidth is 55nm, and the maximum writable range is 250£gm*250£gm. First, we fabricated the 2D photonic crystal microcavity and positioning system on the InGaAs/InAlAs which grown by molecular beam epitaxy (MBE) on InP substrate at 1564nm emission wavelength by E-beam lithography. For the positioning system, we set up a origin point first. And then we design many rectangles whose length is 1£gm, width is 10£gm and gap is 1£gm along X axis and Y axis from the origin point. All of the patterns are regarded as the ruler. Finally, we design a big rectangle whose length is 250£gm and width is 10£gm to adjust the positioning angle above the ruler. The maximum error of the positioning system is 20nm. For the 2D photonic crystal (2D PhC) microcavity, a triangular array of air columns is adopted. The lattice constant and air columns radius are 1150nm and 460nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1535nm~1635nm. We remove signal defect and seven defects in the 2D PhC to form 2D PhC microcavities and the PhC microcavities have many defect modes. The Micro-PL measurement shows when the etching depth was deep enough, the PhC microcavities which have 1-defect and 7-defect appeared defect mode at 1622nm (a/£f=0.74) both. The intensity of 7-defect PhC is 7 times than 1-defect PhC. Both of them cooperate with our simulation and design. And the maximum Q value is about 324 at the defect mode.
10

Fabrication and Analysis of Selectively Liquid-Filled Photonic Crystal Fibers

Liou, Jia-hong 29 June 2009 (has links)
As the photonic crystal fibers (PCFs) are fabricated, it is hard to modulate their optical characteristics to function as tunable optical devices. To introduce tunable optical characteristics into the PCF structures, one can infiltrate liquids into the air holes of the PCFs to form the liquid-filled PCFs. However, the propagation losses become larger due to the finite liquid-hole layers and the lossy liquids infused in all the air holes of the cladding. In this thesis, an efficient full-vector finite-difference frequency-domain (FDFD) mode solver cooperated with the PMLs is utilized to investigate the propagation characteristics of the selectively liquid-filled PCFs. The propagation constants and the propagation losses of the guided modes on the selectively liquid-filled PCFs can be successfully obtained. From our numerical results, the propagation losses of both the internally liquid-filled PCFs and externally liquid-filled PCFs can be efficiently reduced by the outer or inner air-hole layers, and the useful tunablility characteristics for optical device applications can be maintained. Besides, the dispersion-related devices based on the selectively liquid-filled PCFs are also investigated. It is demonstrated that a DFPCF with the flatten dispersion value D within 0 ¡Ó 1 ps/nm/km over £f = 1.45 £gm to 1.65 £gm or a DCPCF with a high negative dispersion value D = -3100 ps/nm/km at £f = 1.55 £gm can be achieved by infiltrating the liquid into all air holes or specified air-hole layers. In the experiment, a simple selectively blocking technique using the microscopy, the tool fiber and the alignment technique is employed to fabricate the internally and externally liquid-filled PCFs. The measurement of the optical characteristics of these selectively liquid-filled PCFs is carried out and compared with the simulation results.

Page generated in 0.0685 seconds