OPTICAL INSTRUMENTATION AND TECHNOLOGY A complex for the fluorescence analysis of macro- and microsamples in the near-infrared P. S. Parfenov, a) A. V. Baranov, A. V. Veniaminov, and A. O. Orlova St. Petersburg State University of Information Technologies, Mechanics, and Optics, St. Petersburg (Submitted July 5, 2010) Opticheski˘ ı Zhurnal 78, 48–52 (February 2011) This paper describes the design features and technical parameters of a complex for characterizing the fluorescence parameters of macro- and microsamples in the near-IR region. Along with the standard 90 ◦ setup for exciting and recording the fluorescence, a microfluorimetric technique is used. Two types of InGaAs photodiodes are compared, and the features of the measurements are discussed, using as an example the recording of the IR fluorescence spectra of PbS quantum dots. c  2011 Optical Society of America. High-precision spectral studies in the near-IR region are indispensable when investigating the fluorescence properties of rare-earth elements in glasses, when creating fiber-optic communication lines, lasers, LEDs, and photodiodes, and when investigating nanostructures that use IR-range quantum dots (PbS, PbSe, PbTe, HgS, etc.) and fundamentally new IR phosphors based on them. 1 The existing technique for studies in the IR region on the whole does not satisfy the modern requirements imposed on fluorescence measurements. The compact spectral devices that have recently appeared, based on the input of exciting radiation by means of an optical fiber, compact dispersive elements, and multichannel detectors, are mainly intended for the characterization of the radiation of lasers and LEDs. 2 , 3 It is difficult to use them for precision analysis of the fluorescence spectra of IR phosphors, such as semiconductor quantum dots with optical transitions in the near IR, because of low sensitivity and inadequate spectral resolution. The traditional approach, based on the use of a monochromator and single-channel recording of the fluorescence, therefore remains crucial. At the same time, the necessity of obtaining spectra from local sections of samples with high spatial resolution requires the use of the microfluorimetry technique, which has undergone very little development in the near-IR region. This paper describes the design features and technical parameters of a complex for characterizing the steady-state fluorescence parameters of macro- and microsamples in the near-IR region (0.8–2.2 μm) with high spectral and spatial resolution. The authors of this article have developed a complex that makes it possible to make measurements both by the standard 90 ◦ excitation/recording setup and using the microfluorimetry technique, where the excitation and reception of the fluo- rescence radiation is carried out using the same microscope objective. According to the standard setup, solutions of substances have been investigated in cells and macrosamples, whereas the microfluorimetry setup is used to visualize microstructured samples and to obtain fluorescence spectra from interesting local sections of the sample. Figure 1 shows a functional diagram of the complex. The illuminator system consists of radiation sources (lasers with wavelengths λ = 532 and 633 nm and power 15 mW and LEDs with emission maxima at wavelengths 520, 590, 625, and 850 nm with power 1 and 3 W), systems of tilting mirrors (TMs), beamsplitters, and a laser-radiation expander. To make measurements using the standard setup (channel I), the exciting radiation of the lasers or LEDs is directed into the sample-cell compartment. The radiation of the fluorescent sample is received at an angle of 90 ◦ , and the image of the horizontal fluorescent region is rotated by 90 ◦ by a Dove prism and is focused on the vertical entrance slit of the monochromator. In the microfluorimeter regime (channel II), only the laser radiation that is directed into the fluorescence microscope by means of a tilting mirror (TM 2) is used to excite the fluorescence. A laser-beam expander is used to fill the aperture of the microscope objective; this is necessary to maximize the spatial resolution. The object is placed on an object stage. A video camera is used to observe an image of the object and to choose the local section of interest of the sample. The radiation is excited and received by means of a high-aperture objective (NA 0.55). The radiation is directed to the entrance slit of the monochromator. In this case, the sample cell and lens L2 are removed from the optical path. The complex is based on an Acton SP-2558 monochro- mator, with relative aperture f /6.5, focal length 500 mm, and a 150 mm −1 diffraction grating, which provides the necessary spectral resolution at fairly high speed. The fluorescence spectrum is recorded by an interchangeable InGaAs photo- diode cooled to −20 ◦ C, mounted behind the exit slit of the monochromator. A 21×0.4 focusing objective is used to match the exit slit of the monochromator with the receiver area of the photodiode (diameter 1 mm). After preamplification, the pho- todiode signal is digitized by a SpectraHub interface module. Two cooled Hamamatsu InGaAs photodiodes are used as detectors—with a standard spectral range (G8605-21, 0.8–1.6 μm) and with an expanded spectral range (G5852-21, 0.9–2.1 μm). 4 The standard photodiode is switched to the bias regime (bias voltage 0.7 V), and this ensures fast response and 120 J. Opt. Technol. 78 (2), February 2011 1070-9762/2011/020120-04/$15.00 c  2011 Optical Society of America 120