Physica E 7 (2000) 367–372 www.elsevier.nl/locate/physe Pressure-induced modulation of the connement in self-organized quantum dots produced and detected by a near-eld optical probe A. Chavez-Pirson * , J. Temmyo, H. Ando NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-0198 Japan Abstract Near-eld optical probing, or nanoprobing, achieves spatial resolution that surpasses the diraction limit of light and makes possible the luminescence imaging and spectroscopy of single quantum dots in dense arrays of dots. We use optical nanoprobing to study self-organized InGaAs quantum dots grown on (3 1 1)B oriented GaAs substrates. Here, we emphasize a new feature of nanoprobing: pressure-induced strain modulation near the surface. Operating in near-eld optical excitation– collection mode, the probe makes contact with the surface and exerts direct pressure whose main eect is a compressive uniaxial strain under the probe. By adjusting the applied pressure, we modulate the local strain environment in and around a quantum dot, but still preserve the capability to capture its near-eld luminescence. Nanoprobe pressure eects modify the connement potential and radiative emission of single quantum dots, and the coupling strength between dots. This opens new possibilities for the study and control of the optical and electronic properties of single- and coupled-quantum dots. ? 2000 Elsevier Science B.V. All rights reserved. PACS: 73.20.Dx; 78.66.Fd; 61.16.Ch; 78.20.Hp Keywords: Quantum dots; Near-eld optics; Pressure eects; Luminescence 1. Introduction Near-eld optical nanoprobing is a powerful method to study the optical properties of self- organized semiconductor quantum dots with spatial resolutions well beyond the diraction limit of light. The high spatial resolution of near-eld optical ber probes, which can approach /40, makes it possi- ble to scan, dot-by-dot, the optical properties of an * Corresponding author. Tel.: 81-462-40-3683; fax: 81-462-70-2342. E-mail address: chavez@wave.brl.ntt.co.jp (A. Chavez-Pirson) entire ensemble of quantum dots. This capability allows both the investigation of array properties and the detailed study of individual quantum dots, and may prove critical for further development of quan- tum dots for use in optical and electronic devices. Op- tical nanoprobing has been successfully used to study excitonic and biexcitonic emission of single-quantum dots from dense arrays of dots [1]. Nanoprobing of quantum dot luminescence produces images with unique polarization-sensitive features attributable to near-eld optical eects [2,3]. Although the images reect the near-eld capturing of dot luminescence by the probe, nanoprobing itself does not perturb 1386-9477/00/$ - see front matter ? 2000 Elsevier Science B.V. All rights reserved. PII:S1386-9477(99)00343-4