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ABSTRACT: This paper reports the theoretical and experimental investigations of the strain sensitive effect of a 2D photonic crystal (PhC) nanocavity resonator for mechanical sensing applications. By using finite element method (FEM) using ANSYS software and finite different time domain (FDTD) simulation using CrystalWave software, the strain sensitivity of a high quality factor PhC nanocavity has been studied. Linear relationships between strain and shift of resonant wavelength of the cavity have been obtained. The sensitivities to longitudinal and transverse strains have been determined to be 1.9 nm/mε and 0.25 nm/mε, respectively. The sample structure were fabricated and characterized. The initial results show that the cavity peak with Q factor estimated to be 3800 had been obtained.
Sensors, 2010 IEEE; 12/2010
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ABSTRACT: We demonstrate a compact silicon photonic crystal Mach-Zehnder interferometer operating in the self-collimation regime. By tailoring the photonic band structure such as to produce self-collimated beams, it is possible to design beam splitters and mirrors and combine these to a 20 x 20 microm(2) format. With transmission spectroscopy we find a pronounced unidirectional optical output, the output ratio being as high as 25 at the self-collimation wavelength. Furthermore, the self-collimated beams and the unidirectionality are clearly observed in real space using near-field and far-field optical microscopy. Interpretation of the optical data is strongly supported by different types of simulations.
Optics Express 03/2010; 18(7):6437-46. · 3.59 Impact Factor
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ABSTRACT: Mode-dependent shifts of resonant frequencies of cavities in liquid crystal (LC) infiltrated planar photonic crystals (PhC) are experimentally observed when the temperature is varied across the LC ordering transition. The shifts can be in opposite directions, even for two very similar nearly degenerate modes. The behavior is attributed to the different interactions of the modes with the two components of the refractive index of the LC infill and directly demonstrates that at least a substantial amount of the LC is oriented perpendicular to the PhC-hole axis.
Applied Physics Letters 12/2009; · 3.84 Impact Factor
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ABSTRACT: The photonic properties of two classes of wavelength-sized cavities are reported for deeply etched InP/InGaAsP/InP planar photonic crystals. The high aspect, deeply etched structures are studied as potential building blocks for nonmembrane type photonic devices in standard InP photonic integrated circuits. The first class consists of cavities of one unit cell in one direction and varying size in the other planar direction. The studied class includes a Fabry–Perot type cavity with one row of missing holes, a simple single missing hole defect cavity, and a cavity consisting of two holes which have been slightly shifted and reduced in hole radius. The best observed quality factor of 65 in this class is obtained for a single hole defect cavity. The second class is comprised of cavities which are derived from a three missing row defect in one direction and varying size in the other direction. This includes a Fabry–Perot type cavity with three rows of missing holes, a point defect cavity consisting of seven unetched holes and a six hole ring cavity. The best observed quality factor of 300 is obtained for the ring cavity in this second class of structures, which is adequate for applications.
Journal of Applied Physics 11/2009; · 2.17 Impact Factor
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ABSTRACT: Tuning of the resonant wavelength of a single hole defect cavity in planar photonic crystals was demonstrated using transmission spectroscopy. Local post-production processing of single holes in a planar photonic crystal is carried out after selectively opening a masking layer by focused ion beam milling. The resonance was blue-shifted by enlargement of selected holes using local wet chemical etching and red-shifted by infiltration with liquid crystals. This method can be applied to precisely control the resonant frequency, and can also be used for mode selective tuning.
Optics Express 11/2009; 17(24):22005-11. · 3.59 Impact Factor
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ABSTRACT: Wavelength-sized point defect cavities coupled to access waveguides are reported for deeply etched InP/InGaAsP/InP two-dimensional photonic crystals. The observed quality factor of 60 is comparable to those found for one-row defect Fabry-Perot cavities and for simple point defect cavities in membranes. The quality factor was changed by varying the number of rows of holes. Upon infiltration of the holes with liquid crystal, frequency tuning was demonstrated.
Optics Letters 07/2009; 34(14):2207-9. · 3.40 Impact Factor
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ABSTRACT: Local post-production processing of single holes in a planar photonic crystal is demonstrated by selectively opening a masking layer by focused ion beam milling. Local tuning was optically demonstrated by both blue-shifting and subsequent red-shifting the resonance frequency of a point defect cavity. Since only a few holes of the PC are affected by the post-processing, the Q-factor is not significantly changed. This method can be applied to precisely control the resonant frequency, and can also be used for mode selective tuning.
Indium Phosphide & Related Materials, 2009. IPRM '09. IEEE International Conference on; 06/2009
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ABSTRACT: We report a new method for the fabrication of sub-10 nm nanopores in a fast single process step. The pore formation is accomplished by exploiting the competition between sputtering and deposition in ion-beam-induced deposition (IBID) on a thin membrane. The pore diameter can be controlled by adjusting the ion beam and gas exposure conditions. The pore diameter is well below the limit that can be achieved by focused ion beam (FIB) milling alone. There is no need of preparation and successive treatments. Apart from simplicity and speed, this method offers an additional advantage of a broad choice of material and thickness of the deposit and the membrane.
Nanotechnology 02/2009; 20(1):015302. · 3.98 Impact Factor
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ABSTRACT: An extensive investigation has been performed on inductively coupled plasma etching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Cl <sub>2</sub> with the addition of N <sub>2</sub> or O <sub>2</sub> for sidewall passivation. The influence of different process parameters such as gas flows, temperature, pressure, ion energy, and inductively coupled plasma power on the hole geometry is presented. It is concluded that photonic crystals can be etched with Cl <sub>2</sub> only; however, temperature and pressure control is critical. Adding passivation gases largely broadens the window in the parameter space for hole etching. Most importantly, etching of narrow holes can be carried out at higher temperatures where the etching is mass limited and spontaneous etching of InP by Cl <sub>2</sub> occurs.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 10/2008; · 1.34 Impact Factor
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ABSTRACT: Remarkable photoluminescence enhancement (PLE) in submonolayer films of PbSe nanocrystals (NCs) upon continuous illumination was observed. The intensity increase from films on InP substrates was highest in vacuum, while for films on Si/SiO2 substrates the PLE was stronger in air. The magnitude of the PLE was found to depend on the excitation intensity, being higher for a weaker irradiation power. The possible mechanisms behind the phenomenon of the PLE are discussed and it is suggested to originate mainly from charge trapping outside the NCs core.
Applied Physics Letters 09/2008; 93(12):121906-121906-3. · 3.84 Impact Factor
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ABSTRACT: Deeply etched InP-based planar photonic crystals incorporating point and line defect structures were fabricated and experimentally investigated. Tuning of the H1 cavity mode and the W3 waveguide mini-stopband by infiltration with the liquid crystal K15 is experimentally demonstrated.
07/2008;
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ABSTRACT: A point defect cavity (H1) was fabricated by deep etching in the InP/InGaAsP/InP system. The optical properties of the devices were experimentally investigated by transmission spectroscopy yielding a Q-factor of ~65. The resonance frequency of the defect cavity was shifted, by infiltrating the surrounding holes with both a polymer and liquid crystal. Furthermore, the transmission was enhanced by a factor > 5 as a result of the filling.
Indium Phosphide and Related Materials, 2008. IPRM 2008. 20th International Conference on; 06/2008
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ABSTRACT: In this paper, Ion Beam Induced Deposition (IBID) mechanisms for nanostructure growth are investigated in terms of the contribution of secondary atoms, secondary electrons, and primary ions.
Microprocesses and Nanotechnology, 2007 Digest of papers; 12/2007
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R. Van der Heijden,
C.F. Carlstrom,
J. A. P. Snijders,
R.W. Van der Heijden,
F. Karouta,
R. Notzel, H.W.M. Salemink,
B. K. C. Kjellander,
C W M Bastiaansen,
D. J. Broer,
E. Van der Drift
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ABSTRACT: Polymer filling of the air holes of Indium Phosphide based two-dimensional photonic crystals is reported. After infiltration of the holes with a liquid monomer and solidification of the infill in situ by thermal polymerization, complete filling is proven using scanning electron microscopy. Optical transmission measurements of a filled photonic crystal structure exhibit a redshift of the air band, confirming the complete filling. Comment: To be published in Appl. Phys. Lett
03/2006;
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ABSTRACT: We have investigated ICP-etching of deep photonic crystal holes in InP using solely Cl<sub>2</sub> as supplied etching gas. The influence of process parameters on hole geometry is discussed and optical test results are reported
Indium Phosphide and Related Materials, 2005. International Conference on; 06/2005
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ABSTRACT: We have fabricated two-dimensional photonic crystals in InP-based materials with Cl<sub>2</sub>-based inductively coupled plasma etching. To obtain vertical sidewalls, we employ sidewall passivation through addition of N<sub>2</sub> or O<sub>2</sub> to the plasma. With the Cl<sub>2</sub>O<sub>2</sub>-process we are able to etch 3.2 μm deep holes that have nearly cylindrical shape in the upper 2 μm. The first optical results illustrate the feasibility of our approach, showing over 30 dB transmission reduction in the ΓK-stopband.
Indium Phosphide and Related Materials, 2005. International Conference on; 06/2005
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ABSTRACT: We have investigated the effect of Inductively Coupled Plasma (ICP) etching using a C12-CHrH2 chemistry on the surface morphology of InP substrates. We have observed a strong dependence of the surface morphology on the etching times of semi-insulating (s i) InP-wafers. Pillars are formed after a sufficient etching time. Photoluminescence characterization revealed a strong correlation between morphology and PL signal intensity.
04/2004;
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ABSTRACT: Scanning-tunneling microscope induced luminescence at low temperature has been used to study the carrier injection into single self-assembled InGaAs/GaAs quantum dots. Electrons are injected from the tip into the dots, which are located in the intrinsic region of a p-i-n junction, and contain excess holes under typical operational conditions. Only a fraction ( ∼ 4%) of the dots is found to be optically active under local electrical excitation. Spatial dependent measurements indicate a highly nonhomogeneous electron diffusion towards the dots. By analyzing the spatial dependence of individual peaks in the measured spectra, the contributions of individual dots to the total, multidot spectrum can be disentangled. © 2003 American Institute of Physics.
Applied Physics Letters 07/2003; 83(2):290-292. · 3.84 Impact Factor
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ABSTRACT: Structures containing stacked self-assembled InAs quantum dots within a GaAs matrix are studied by cross-sectional scanning tunneling microscopy. The dots consist of an InGaAs alloy with an increasing indium concentration in the growth direction. From comparison of the lattice constant profiles of stacked and unstacked dots, it is evident that the strain in the GaAs matrix around the dots is strongly affected by the stacking process. The results show an increasing deformation of the dots in the stack and a reduced growth rate of the GaAs spacer layers, resulting in the formation of terraces on the growth surface on which new dots form. If the total structure, containing the dot layers and the spacer layers, exceeds 30 nm, the local GaAs growth rate remains constant from this point on. The InAs dot growth rate remains constant throughout the entire stack. © 2003 American Institute of Physics.
Applied Physics Letters 05/2003; 82(21):3758-3760. · 3.84 Impact Factor
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ABSTRACT: Scanning-tunneling spectroscopy experiments have been performed on conjugated polymer films and have been compared to a three-dimensional numerical model for charge injection and transport. It is found that field enhancement near the tip apex leads to significant changes in the injected current, which can amount to more than an order of magnitude, and can even change the polarity of the dominant charge carrier. As a direct consequence, the single-particle band gap and band alignment of the organic material can be directly obtained from tip height-voltage (z-V) curves, provided that the tip has a sufficiently sharp apex.
MRS Proceedings. 12/2002; 771.
