Quoc Hung Phan

Surface plasmon resonance prism coupler for enhanced circular dichroism sensing.

A novel method for enhanced circular dichroism (CD) detection is proposed based on a surface plasmon resonance (SPR) prism coupler and a polarization scanning ellipsometry technique. An analytical model is derived to extract the CD and degree of polarization (DOP) properties of optical samples with and without scattering effects, respectively. The validity of the analytical model is confirmed by means of numerical simulations. The simulation results show that the proposed detection method has a sensitivity of 10-5~10-6 RIU (refractive index unit) for refractive indices in the range of 1.32~1.36 and 1.3100~1.3118. The practical feasibility of the proposed method is demonstrated by the experimental results for the sensitivity of the CD with the chlorophyllin samples with/without scattering effect. It is shown that for both types of sample, the extracted CD value increases linearly with the chlorophyll concentration over the considered range. In general, the results obtained in this study show that the measured CD response is highly sensitive to the polarization scanning angle. Consequently, the potential of polarization scanning ellipsometry for high-resolution CD detection is confirmed.

Differential Mueller matrix polarimetry technique for non-invasive measurement of glucose concentration on human fingertip

A differential Mueller matrix polarimetry technique is proposed for obtaining non-invasive (NI) measurements of the glucose concentration on the human fingertip. The feasibility of the proposed method is demonstrated by detecting the optical rotation angle and depolarization index of tissue phantom samples containing de-ionized water (DI), glucose solutions with concentrations ranging from 0~500 mg/dL and 2% lipofundin. The results show that the extracted optical rotation angle increases linearly with an increasing glucose concentration, while the depolarization index decreases. The practical applicability of the proposed method is demonstrated by measuring the optical rotation angle and depolarization index properties of the human fingertips of healthy volunteers.

Characterization of optical/physical properties of anisotropic thin films with rough surfaces by Stokes-Mueller ellipsometry

A decomposition model with depolarization matrix is proposed to characterize the optical and physical properties of anisotropic thin films with rough surfaces. In the proposed approach, the refractive index and thickness of the thin film are inversely extracted using a pure polarization matrix, and the surface roughness of the film is characterized using a depolarization matrix. The validity of the proposed method is demonstrated by comparing the experimental results for the refractive index and thickness of a thin film with the analytical results obtained using the effective ellipsometric parameters of the film. The results show that the proposed method provides a reliable means of obtaining the optical and physical properties of thin films with fine or coarse rough surfaces. Importantly, the proposed method not only enables the coarse surface roughness of thin-film samples to be determined in a non-contact optical manner, but also provides a more versatile approach than the well-known effective medium approximation (EMA) model, which is restricted to the characterization of samples with low surface roughness.

Characterization of voltage-driven twisted nematic liquid crystal cell by dynamic polarization scanning ellipsometry.

A dynamic polarization scanning ellipsometry technique based on Stokes polarimetry is proposed for dynamically characterizing a voltage-driven twisted nematic liquid crystal (TNLC) cell. In the proposed method, the six effective ellipsometric parameters are extracted under modulation voltages ranging from 0 V ~ + 10 V using four linearly polarized input lights. The profiles of the tilt angle and twist angle are calculated as a function of the modulation voltage. The validity of the proposed method is confirmed by comparing the experimental results for the effective ellipsometric parameters of a TNLC cell with the analytical results. Furthermore, a genetic algorithm (GA) based on a curve-fitting technique is used to inversely extract the pretilt angle, twist angle and rubbing direction of the TNLC cell. These extracted values are then compared to the known valued of the TNLC cell. In general, the results presented in this paper show that the proposed method provides a reliable means of obtaining the dynamic optical properties of a TNLC cell.

A system for full Stokes vector measurement for low concentration glucose sensing

A high performance system for full Stokes vector measurements was developed. The proposed system comprised a polarization scanning generator (PSG) and a high accuracy polarization state analyzer (PSA) was proposed. The PSG generated full state of polarization of light by using voltage driven electro-optics modulator without using any mechanical moving parts. The PSA was employed to record the intensity of output polarized lights in a high speed manner. The accuracy of proposed system was 10-4 for all Stokes vector (S0, S1, S2, S3) measurements in the full state of polarization of lights. An application of proposed system for low concentration glucose in aqueous solution sensing with/without scattering effects was demonstrated. The sensitivity of the optical rotation angle of CB property to changes in the concentration of glucose sample was examined over the range from 0 to 0.5g/dl. The results confirm that the proposed system is able to detect glucose at fine concentration of 0.02g/dl. The linear variation of the optical rotation angle and different glucose concentration at different scattering effects was obtained. In general, the new measurement system proposed in this study provided a fast and reliable method to measure all Stokes vectors and its potential applications in biological sensing.

Differential Mueller matrix polarimetry for low concentration of glucose sensing

A novel of glucose sensing method based on differential Mueller matrix polarimetry is proposed. An analytical model is derived for extracting the optical rotation angle (γ) and degree of depolarization properties (Δ) of glucose sample with scattering affects. The practical feasibility of the proposed method is demonstrated by the experimental results for the sensitivity of the γ and Δ with the glucose samples with 2% phantom particles. The results show that the extracted valued of γ and Δ vary linearly with the glucose concentration over the measured range of 0 to 100 mg/dl with lowest increment of 20 mg/dl. In general, the proposed technique provides a reliable and simple method for low concentration of glucose sensing.

Surface plasmon resonance prism coupler for enhanced circular dichrosim/birefringence sensing

A novel method for surface plasmon resonance (SPR) enhanced circular dichroism (CD), circular birefringence (CB), and degree of polarization (Dep) detection is proposed using Stokes-Mueller matrix polarimetry technique. The validity of the analytical model is confirmed by means of numerical simulations, and the simulation results show that the proposed detection method for CB and CD has a sensitivity of 10-5 RIU and 10-4 RIU (refractive index unit) for refractive indices in the range of 1.3~1.4, respectively. The practical feasibility of the proposed method is demonstrated by the experimental results for detecting the CB/CD/Dep with the glucose-chlorophyllin compound samples contained polystyrene microsphere particles. It is shown that the extracted CB value decreases linearly with glucose concentration over the considered range while the extracted CD value increases linearly with the chlorophyll concentration over the considered range. In general, the results obtained in this study show that the measured CB and CD response is highly sensitive to the polarization scanning angle. Consequently, the potential of Stokes-Mueller matrix polarimetry for highresolution in CB/CD/Dep detection is confirmed.

Stokes–Mueller matrix polarimetry technique for circular dichroism/birefringence sensing with scattering effects

Abstract. A surface plasmon resonance (SPR)-enhanced method is proposed for measuring the circular dichroism (CD), circular birefringence (CB), and degree of polarization (DOP) of turbid media using a Stokes–Mueller matrix polarimetry technique. The validity of the analytical model is confirmed by means of numerical simulations. The simulation results show that the proposed detection method enables the CD and CB properties to be measured with a resolution of 10−4 refractive index unit (RIU) and 10−5  RIU, respectively, for refractive indices in the range of 1.3 to 1.4. The practical feasibility of the proposed method is demonstrated by detecting the CB/CD/DOP properties of glucose–chlorophyllin compound samples containing polystyrene microspheres. It is shown that the extracted CB value decreases linearly with the glucose concentration, while the extracted CD value increases linearly with the chlorophyllin concentration. However, the DOP is insensitive to both the glucose concentration and the chlorophyllin concentration. Consequently, the potential of the proposed SPR-enhanced Stokes–Mueller matrix polarimetry method for high-resolution CB/CD/DOP detection is confirmed. Notably, in contrast to conventional SPR techniques designed to detect relative refractive index changes, the SPR technique proposed in the present study allows absolute measurements of the optical properties (CB/CD/DOP) to be obtained.