Optimization of linear-wavenumber spectrometer for high-resolution spectral domain optical coherence tomography

Nonlinear detection of the spectral interferograms in wavenumber (k) space degrades the depth-dependent signal sensitivity in conventional linear-in-λ spectrometer based spectral domain optical coherence tomography (SDOCT). Linear-k spectrometer enables high sensitivity SDOCT imaging without the need of resampling the digitized non-linear-in-k data. Here we report an effective optimization method for linear-k spectrometer used in a high-resolution SDOCT system. The design parameters of the linear-k spectrometer, including the material of the dispersive prism, the prism vertex angle, and the rotation angle between the grating and prism, are optimized through the numerical simulation of the spectral interference signal. As guided by the optimization results, we constructed the linear-k spectrometer based SDOCT system and evaluated its imaging performances. The axial resolution of the system can be maintained to be higher than 9.1μm throughout the imaging depth range of 2.42 mm. The sensitivity was experimentally measured to be 91 dB with −6 dB roll-off within the depth range of 1.2 mm.