Photons were generated possessing orbital angular momentum (OAM) in the form of Laguerre-Gaussian (LG) laser modes. Three Mach-Zehnder interferometer systems, with the use of Dove prisms, were constructed to sort and detect the LG modes based on their OAM state. Successful generating, sorting, and detecting of LG modes is the first step towards information encoding and decoding via lasers. It is possible to generate many LG modes, which can be orthogonally decoded. With many modes to encode information with it is possible to transfer more than one bit of information with a single photon using LG encoding. An experimental test of this concept was performed by demonstrating the generation and sorting of LG modes with attenuated intensities averaging below one photon passing through the system at a time. In summary, generating, sorting, and low-power detecting of specific LG modes were all demonstrated.
A novel immunoadjuvant, glycated chitosan, has been used in combinations with a near-infrared laser and a laser- absorbing dye to treat metastatic tumors in rats. The laser-dye combination provides selective photothermal tumor destruction. The addition of the in situ immunoadjuvant works in tandem with the photothermal interaction to induce a host antitumor immunity. Our previous experiments have shown the efficacy of this novel modality against a metastatic breast cancer in rat model, using the three components. The current study is to investigate the roles of different components, namely, the laser, the dye and the immunoadjuvant. Firs, the selective photothermal laser- tissue interactions are studied in vivo using rat leg muscles and rat tumors. Our results showed that with appropriate combination of laser parameter and dye does, an optimal selective photothermal tissue interaction could be achieved. The immune response is crucial in control of tumor metastasis and the immunoadjuvant has played pivotal role in the induction of the immunity in our experiment. Therefore, the role of immunoadjuvants in the laser cancer treatment is also investigated in the current study. Specifically, three different concentrations of glycated chitosan solutions - 0.5%, 1% and 2% - were used. In comparison, the 1% solution provided the best treatment outcome. Two additional immunoadjuvants, incomplete Freund's adjuvant and complete Freund's adjuvant were also used in the same laser-dye-adjuvant treatment protocol. The functions of different adjuvants are compared.
Responses of tissue to laser stimulation are crucial in both disease diagnostics and treatment. In general, when tissue absorbs laser energy photothermal interaction occurs. The most important signature of the photothermal reaction is the tissue temperature change during and after the laser irradiation. Experimentally, the tissue reaction to laser irradiation can be measured by numerous methods including direct temperature measurement and measurement of perfusion change. In this study, a multiple-channel temperature probe was used to measure tissue temperature change during irradiation of lasers with different wavelengths at different power settings. Tissue temperature in chicken breast tissue as well as skin and breast tumor of rats was measured during irradiation of an 805-nm diode laser. The vertical profiles of temperature were obtained using simultaneous measurement at several different locations. The absorption of laser energy by tissue was enhanced by injecting laser-absorbing dye into the tissue. A Nd:YAG laser of 1064-nm wavelength was also used to irradiate turkey breast tissue. Our results showed that both laser penetration ability and photothermal reaction depended on the wavelength of lasers. In the case of 805-nm laser, the temperature increased rapidly only in the region close to the laser source and the thermal equilibrium could be reached within a short time period. The laser absorbing dye drastically enhanced the thermal reaction, resulting in approximately 4-fold temperature increase. On the contrary, the laser beam with 1064-nm wavelength penetrated deeply into tissue and the tissue temperature continued increasing even after a 10-minute laser irradiation.
Fluorescence spectroscopy of diseased tissues, including chemical-induced rat liver, kidney and testis lesions, as well as murine mammary tumor, was studied. The rat liver, kidney and testis tissues were excited by radiation of 350 and 366 nm, which appeared to provide the optimal differentiation between normal and lesion tissues; the tumor tissues were excited by both 350 nm and 775 nm wavelengths. In comparison with normal liver tissue, at (lambda) ex equals 366 nm, the fluorescent spectrum of liver lesion showed a clear red shift around the emission peak of 470 nm, the major native fluorescent peak of organized tissue. When excited by 350 nm wavelength, all the chemically induced lesion tissues (liver, kidney and testis) appeared to cause a significant reduction of emission intensity at the 470 nm peak. While the 775 nm excitation did not reveal any significant difference among tumor, muscle and skin tissues, the 350 nm excitation did provide some interesting features among the tumor tissues at different stages. Compared with muscle tissue, the viable tumor showed an overall reduction of emission intensity around 470 nm. In addition, the viable tumor tissue showed a secondary emission peak at 390 nm with necrotic tumor tissue having a reduced intensity. The histology of both viable and necrotic tumor tissue was examined and appeared to correlate with the results of the fluorescent spectroscopy observation.