We present a lamellar grating interferometer realized with microelectromechanical system technology. It is used as a time-scanning Fourier-transform spectrometer. The motion is carried out by an electrostatic comb drive actuator fabricated by silicon micromachining, particularly by silicon-on-insulator technology. For the first time to our knowledge, we measure the spectrum of an extended white-light source with a resolution of 1.6 nm at a wavelength of 400 nm and of 5.5 nm at 800 nm. The wavelength accuracy is better than 0.5 nm, and the inspected wavelength range extends from 380 to 1100 nm. The optical path difference maximum is 145 mm. The dimensions of the device are 5 mm 3 5 mm.Spectrometry is widely used in industry and research laboratories. There are many different methods that are used in a variety of fields. In particular, Fourier-transform spectroscopy is a powerful technique for investigating weak sources with high resolution. At present, an extended range of Fourier spectrometers is commercially available. However, high resolution involves an elevated degree of mechanism precision and therefore large size and high cost. Recently, lower-resolution miniature spectrometers have become attractive because of new applications, expanding opportunities in a remarkable variety of disciplines and industries.

We present a lamellar grating interferometer (LGI) realized by silicon micro-machining. The LGI is a binary grating with a variable depth. The motion is carried out by an electrostatic comb drive actuator fabricated by silicon-oninsulator (SOI) technology. It is used as Fourier transform spectrometer (FTS). We have measured an optical path difference maximum of 82 µm. The measured resolution of the spectrometer after the phase correction is 6 nm at a wavelength of 633 nm. A preliminary measurement with a xenon arc lamp is shown.A lamellar grating interferometer (LGI) is a grating that operates in the zeroth order. This particular type of apparatus was invented by Strong [1]. A scheme of the principle is illustrated in Fig. 1a. The LGI is used as FTS, but contrary to the Michelson interferometer that splits wave amplitudes at the beamsplitter, the LGI divides the wavefront. At the grating, the wavefront is divided such that one half of the beam is reflected from the front facets (fixed mirrors in Fig. 1b) and one half from the back facets (mobile mirrors in Fig 1b). The distance d between the two series of mirrors determines the optical path difference (OPD = 2d) between the two parts of the wave. The enormous advantage of this configuration, compared with a Michelson interferometer, is the absence of a beamsplitter. Indeed, any additional micro-optical component is a limitation in the particular case of micro-sized spectrometers. In general, this type of spectrometer is used for wavelengths larger than 100 µm; below, the tolerances are too tight for most machine shops. Silicon micromachining is the ideal technology to overcome these limitations for shorter wavelengths. where a is the grating period, α is the diffraction angle, λ is the wavelength, andis the phase delay introduced by the displacement d. At the zeroth order of the grating (α = 0), Eq. (1) To characterize the performance of our device, we have recorded the zeroth order I 0 (d) of the diffraction pattern produced by a collimated HeNe laser on the grating. To get rid of the non-linearity of the driving system, a phase correction is effectuated. The phase correction is described in reference [3]. We have measured an OPD nonlinearity ∆ OPD of ±0.6 µm for a displacement of 82 µm. Figure 2 shows the spectrum of a He-Ne laser before and after the phase correction. The measured resolution of the spectrometer after the phase correction is 6 nm at a wavelength of 633 nm. To achieve the maximum displacement, we have applied a variable voltage V 0 of ±8.5 V and the constant tensions V A and V B were 85 V, respectively -91 V. In addition, measurements with an extended white light source have been carried out. Figure 3 shows the interferogram and the spectrum of a xenon low-pressure arc lamp. In this experiment, the light coming from a multimode fiber is collimated and then focused with a cylindrical

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