We show that the SU-8 epoxy resist can be exposed by two-photon absorption at 4 K, allowing spectroscopy and lithography to be performed by the same apparatus. We present a systematic study of the exposure parameters.

We have registered the position of single InGaAs spectroscopy, and the creation of alignment markers by laser quantum dots using a novel cryogenic laser photolithography photolithography at 4K [6]. Markers are created by two-photon technique. This would be useful in realizing solid state cavity absorption (TPA) laser photolithography of SU-8, a negative quantum electrodynamics. By fabricating metal alignment photoresist widely used in the micro-electromechanical markers around the quantum dot, it was registered with an systems community [7]. TPA photolithography exploits accuracy of 50 nm. Following the marker fabrication process we nonlinear absorption by SU-8 of high-peak-power laser pulses demonstrated that the same quantum dot was reacquired, with at a wavelength that is too long to expose the resist by singlean accuracy of 150 nm. The photoluminescence spectra from the photon absorption [8]. Advantages of this techufique are that it quantum dots before and after processing were identical except does not rely on chance and is therefore suitable for lowfor a small red shift (-4 nm), probably introduced during the density QD samples, and allows the selection of QDs with reactive ion etching. desired properties (e.g. wavelength, lifetime). In this paper we Keywords-Nanotechnology; Photoluminescence; Quantum discuss the details of the QD registration process, investigate effectsemicon.ductordevices its accuracy and report on the progress towards fabricating devices using these registered QDs. I. INTRODUCTION II. FABRICATION PROCESSQuantum information processing represents a new paradigm in information science, with the elementary unitThe registration process consists of four steps: 1) being the quantum bit (qubit). Solid state systems such as Preparation of a metal layer with clear apertures on the sample; excitons or spin states in quantum dots (QDs) have attracted 2) gPL spectroscopy to locate a QD within an aperture; 3) much attention as potential qubits as it provides advantage of Laser exposure of a resist layer to define alignment markers in scalability and long coherence time [1]. A common feature in the surrounding metal; 4) Fabrication of the alignment markers. many of these schemes has been the requirement for the Figure 1 illustrates this process. A metallic mask was generation of single-photons on-demand [2]; with many solid fabricated on the surface of a low density (_108 cm-2) InGaAs state devices/experiments exploiting cavity quantum electrodynamics (CQED) consisting of QDs positioned in (a) Tumn(..gsn optically structured microcavities [1,[3][4][5]. A key requirement to achieving effective coupling between the cavity mode and the QD exciton is the accurate alignment; the electric field anti-(+100 nm). To date, most solid state CQED devices have relied @4()ocpy sist on chance to achieve alignment between randomly positioned QDs and the cavity. For example, Yoshicet al.[3] fabricated -30,000 photonic crystal nanocavities on a high density QD sample (-3.5 x i010 cm2). The low yields (< 1%) inherent i...

We discuss a novel technique to register the spatial and spectral characteristics of a single quantum dot using two photon absorption laser lithography. This would be useful in realizing solid state cavity quantum electrodynamics.Index Terms -Nanotechnology, photoluminescence, quantum effect semiconductor devices.

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