A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filters working at 1,300 nm center wavelength is proposed.The combined filters consist of a fiber FabryPerot tunable filter and a tunable filter based on diffractive grating with scanning polygon mirror.In contrast to traditional method using single tunable filter,the trade-off between bandwidth and instantaneous line-width is alleviated.Parallel implementation of two semiconductor optical amplifiers with different wavelength range is adopted in the laser resonator for broadband light amplification.The Fourier domain mode locking swept laser source with combined tunable filters offers broadband tunable range with narrow instantaneous line-width,which is especially benefiting for high-quality optical frequency domain imaging.The proposed Fourier domain mode locking swept laser source provides a tuning range of 160 nm with instantaneous line-width of about 0.01nm at sweeping rate of 15 kHz,a finesse of 16,000 is thus achieved.
MINGHUI CHENZHIHUA DINGLING WANGTONG WUYUANHAO TAO
Cancer(malignant tumor)is one of the serious threats to human life,causing 13%of all human deaths.A crucial step in the metastasis cascade of cancer is hematogenous spreading of tumor cells from a primary tumor.Thus,isolation and identification of cells that have detached from the primary tumor and circulating in the bloodstream(circulating tumor cells,CTCs)is considered to be a potential alternation to detect,characterize,and monitor cancer.Current methods for isolating CTCs are limited to complex analytic approaches that generate very low yield and purity.Here,we propose a high throughput 3D structured microfluidic chip integrated with surface plasmon resonance(SPR)sensor to isolate and identify CTCs from peripheral whole blood sample.The microfluidic velocity-field within the channel of the chip is mediated by an array of microposts protruding from upper surface of the channel.The height of microposts is shorter than that of the channel,forming a gap between the microposts and the lower surface of the channel.The lower surface of the channel also acts as the SPR sensor which can be used to identify isolated CTCs.Microfluidic velocity-field under different parameters of the arrayed microposts is studied through numerical simulation based on finite element method.Measurement on one of such fabricated microchips is conducted by our established optical Doppler tomography technique benefiting from its noninvasive,noncontact,and high-resolution spatialresolved capabilities.Both simulation and measurement of the microfluidic velocity-field within the structured channel demonstrates that it is feasible to introduce fluidic mixing and causes perpendicular flow component to the lower surface of the channel by the 3D structured microposts.Such mixing and approaching capabilities are especially desirable for isolation and identification of CTCs at the coated SPR sensor.
Axial superresolution in optical coherence tomography(OCT)by a three-zone annular phase¯lter is demonstrated.In the proposed probe of a spectral domain OCT system,the width of the central lobe of the axial intensity point spread function is apodized by the¯lter to be within the coherence gate determined by the light source,while its sidelobes are lying outside the coherence gate without contributing to the coherence imaging.By measurement of the depth response of the OCT system before and after inserting the¯lter,an improvement of about 20%in axial resolution is conrmed.OCT imaging on biological sample of orange fresh is also conducted,demonstrating increased depth discrimination without the negative contribution from sidelobes realized by the phaselter in combination with the coherence gate intrinsic to OCT.It comes to a conclusion that we can obtain axial superresolution by¯lter in OCT system without the degrading in°uence of large sidelobes.
A swept-source optical coherence tomography(SSOCT)system based on a high-speed scanning laser source at center wavelength of 1320 nm and scanning rate of 20 kHz is developed.The axial resolution is enhanced to 8.3μm by reshaping the spectrum in frequency domain using a window function and a wave number calibration method based on a Mach-Zender Interferometer(MZI)integrated in the SSOCT system.The imaging speed and depth range are 0.04 s per frame and 3.9 mm,respectively.The peak sensitivity of the SSOCT system is calibrated to be 112 dB.With the developed SSOCT system,optical coherence tomography(OCT)images of human finger tissue are obtained which enable us to view the sweat duct(SD),stratum corneum(SC)and epidermis(ED),demonstrating the feasibility of the SSOCT system for in vivo biomedical imaging.
