In this Letter, the amplitude and group delay characteristics of coupled resonator optical waveguides apodized through the longitudinal offset technique are presented. The devices have been fabricated in silicon-on-insulator technology employing deep ultraviolet lithography. The structures analyzed consisted of three racetracks resonators uniform (nonapodized) and apodized with the aforementioned technique, showing a delay of 5 AE 3 ps and 4 AE 0:5 ps over 1.6 and 1:4 nm bandwidths, respectively. © 2011 Optical Society of America OCIS codes: 130.3120, 230.5750.Coupled resonator optical waveguides (CROWs) [1] have been extensively studied in the past [2,3]. It is well known that the CROW response presents ripples when the devices are designed for all the couplers to have the same coupling constant. The method to overcome ripples and produce boxlike filtering responses is to set different coupling constants for the couplers, following wellknown windowing techniques used in digital filter design [4]; however, this is the most complicated part from a fabrication perspective. The control over the coupling constants of CROW devices has been done typically by changing the lateral distance between consecutive resonators at a scale of tens of nanometers [5]. To achieve high precision, fabrication techniques as electron-beam patterning are required, at the cost of less device yield per time compared to other techniques, such as photolithography, which in turn have worse resolution (hundreds of nanometers).In our previous work, we have presented the apodization of CROWs through a novel technique, the longitudinal offset technique [6], where the change in the coupling constants for each cavity in the CROW structure is accomplished by applying a longitudinal offset between the resonators, instead of the conventional transversal offset. This technique alleviates the fabrication requirements, as the change in each stage of the CROW can be 2 orders of magnitude higher than with the conventional techniques. Therefore, it is suitable for mass production fabrication procedures, such as photolitographic systems [7]. In this Letter, we present, to the best of our knowledge, the first practical demonstration of the aforementioned longitudinal offset technique. Figure 1 shows scanning electron microscope (SEM) images of the uniform and apodized CROW devices, respectively, fabricated in silicon-on-insulator technology using deep ultraviolet (DUV) lithography [8]. The silicon photonic wire waveguide, on top of a 2-μm-thick BOX layer, is 530 nm wide by 220 nm thick in order to ensure TE monomode propagation. The racetracks have a bend radius R ¼ 5 μm and a straight section L s ¼ 53:3 μm in both devices. The measured linear propagation loss in such photonic wires is 6 AE 1 dB=cm, and the group index around the 1:55 μm wavelength is n g ≃ 4:25 and has been derived from the free spectral range (FSR) of the CROW devices. The measured FSR near the 1:55 μm wavelength was 4:09 nm. The gaps between cavities in the uniform and apodized CROWs have...