The possibility to pattern III-V compound semiconductor with nanometer scale is of great interest to photonic, electronic
and optoelectronic systems. Typical method for sub-micrometer compound semiconductor dry etching utilizes PMMA
or other resist to transfer patterns to SiO2 as intermediate masks due to resist's low etching selectivity, especially for ultra-small features. This additional pattern transfer will inevitably increase the potential damage caused by plasma dry
etching and the complexity of patterning process. Therefore, it is desirable to find an easier and more effective way to
pattern compound semiconductor. In this paper, we report a new approach of direct pattern transfer using Ti(OBun)4 solgel derived TiO2 resist as mask. The optimal dose of TiO2 resist for e-beam lithography is ~220mC/cm2. Thermal
stability study of spin-coated TiO2 shows a good performance as lithography resist even at 300°C, which will have
wider applications than conventional resists. Post-annealings at different temperatures are performed to study
temperature-dependence of patterned TiO2 resist as dry-etching mask. The etching selectivity of sample InP compound semiconductor to TiO2 resist is over 7:1. A variety of sub-100 dry etching patterns with good profile qualities have been obtained. The aspect ratio of etching patterns is over 20:1, and the smallest feature is as small as 20nm with over 600nm deep. This sol-gel derived TiO2 sipn-coatable nanolithography resist with high etching selectivity and high aspect ratio etching profile provides a novel and convenient way to directly pattern compound semiconductor material for various challenging nano sacle photonic, electronic and optoelectronic applications.
The possibility of imaging objects at the resolution of smaller than the optical diffraction limit is of great interest to
nanotechnologies and biotechnologies. In this paper, we present a novel near-filed nano-imaging device based on
nanophotodetector(NPD) array, which is capable of addressing function. Multi-level Multi-electron(MLME) Finitedifference
time-domain(FDTD) method is used to simulate the performance of NPD array. The simulation shows a
highest obtainable resolution of 150nm for the light with 1.55μm wavelength. Various photolithography, e-beam
lithography and etching back techniques have been developed to realize the NPD device. Up to 4x4 slab version NPD
array with various resolutions have been successfully realized. The smallest pixel size is as small as 150nm.
Fabry-Perot etalons using electro-optic (EO) organic materials can be used for devices such as tunable
filters and spatial light modulators (SLM's) for wavelength division multiplexing (WDM) communication
systems1-5 and ultrafast imaging systems. For these applications the SLM's need to have: (i) low insertion
loss, (ii) high speed operation, and (iii) large modulation depth with low drive voltage. Recently, there have
been three developments which together can enhance the SLM performance to a higher level. First, low
loss distributed Bragg reflector (DBR) mirrors are now used in SLM's to replace thin metal mirrors, resulting
in reduced transmission loss, high reflectivity (>99%) and high finesse. Second, EO polymer materials
have shown excellent properties for wide bandwidth optical modulation for information technology due to
their fabrication flexibility, compatibility with high speed operation, and large EO coefficients at
telecommunication wavelengths. For instance, the EO polymer AJL8/APC (AJL8: nonlinear optical
chromophore, and APC: amorphous polycarbonate has recently been incorporated into waveguide
modulators and achieved good performance for optical modulation. Finally, very low loss transparent
conducting oxide (TCO) electrodes have drawn increasing attention for applications in optoelectronic devices.
Here we will address how the low loss indium oxide (In2O3) electrodes with an absorption coefficient
~1000/cm and conductivity ~204 S/cm can help improve the modulation performance of EO polymer
Fabry-Pérot étalons using the advanced electro-optic (EO) polymer material (AJL8/APC). A hybrid etalon
structure with one highly conductive indium tin oxide (ITO) electrode outside the etalon cavity and one
low-absorption In2O3 electrode inside etalon cavity has been demonstrated. High finesse (~234), improved
effective applied voltage ratio (~0.25), and low insertion loss (~4 dB) have been obtained. A 10 dB
isolation ratio and ~10% modulation depth at 200 kHz with only 5 V applied voltage have been achieved.
These results indicate that such etalons are very promising candidates for ultrafast spatial light modulation in
In this paper, we present a novel device structure for organic electro-optic modulators using transparent conducting oxides (TCOs) as electrodes to substantially reduce the switching voltage, and describe their fabrication. We report two different types of device geometry, a top conducting and a side conducting geometry, and discuss their strengths and weaknesses. We discuss how the voltage and speed performance of such modulators are dependant on the conductivity/optical loss ratio of the TCO electrodes. Our device simulation shows that by appropriately engineering the high TCO conductivity/optical loss ratio, 4-6x lower switching voltage can be achieved while still maintaining high modulation frequencies and low optical loss. We show that certain new TCO materials are capable of achieving the high conductivity/optical loss required for efficient modulation in the 1300-1550 nm wavelength range. We summarize the optical loss characteristics at 1300 nm of different types of thin-film TCO materials grown using different deposition techniques. TCO electrodes based on different types of materials, such as In2O3, ZnO, and ITO have been investigated for our device structures. Fabrication issues associated with the deposition of TCO electrodes directly on organic EO materials and our approach to addressing them are discussed. Initial results for organic EO modulators fabricated with TCOs as electrodes are presented, and the performance of these modulators are compared with theoretical modeling results. The new device structures presented here will enable next generation low-voltage organic EO modulators targeting RF photonics applications.