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Objective: 5-aminolevulinic acid (5-ALA) is a precursor of the photosensitizer Protoporphyrin IX (PpIX) and photodynamic therapy (PDT) with 5-ALA has been used in clinical practice. However, tumor cellular hypoxia severely affects the efficiency of photodynamic therapy. In this study, photodynamic therapy was combined with tirapazamine to investigate the effects of the combined intervention and the related mechanisms it may involve. Methods: Colony formation assays were used to demonstrate cell proliferation. Transwell assays were performed to observe the effect on cell invasion and metastasis after the corresponding intervention. DCFH-DA probe was used to detect the reactive oxygen species content. Flow cytometry was used to detect the effects of the interventions on apoptosis and cell cycle. The relevant pathways that may be involved are explored by examining the expression levels of the relevant proteins and genes. Results: Colony formation assays indicated that the combined intervention inhibited cell proliferation. Transwell assays demonstrated that PDT combined with TPZ effectively inhibited tumor cell invasion and metastasis. In addition, fluorescence intensity generated by DCFH-DA oxidation was detected indicating that the combined intervention increased the formation of reactive oxygen species. Flow cytometry clearly showed that the combination of PDT and TPZ further increased apoptosis and cell cycle arrest. The results of western blotting and qRT-PCR experiments confirmed that the combination therapy inhibited HIF-1α/VEGF axis and the PI3K/Akt/mTOR pathway activation. Conclusion: 5-ALA-PDT combined with TPZ can inhibit cell proliferation, increase apoptosis, and inhibit the PI3K/Akt/mTOR pathway, thus inhibiting tumor growth and metastasis and improving anti-cancer effects.

BackgroundsAdvanced ovarian cancer is frequently accompanied by extensive peritoneal metastasis, complicating surgical interventions. This study aims to explore the application of 3D reconstruction and 3D printing technology in the treatment of advanced ovarian cancer.MethodsWe conducted a retrospective analysis of 60 patients with stage III ovarian cancer who underwent cytoreductive surgery at Hebei University Affiliated Hospital between 2020 and 2023. Patients were randomly assigned to three groups: a 3D visualization group, a 3D visualization plus 3D printing group, and a traditional 2D CT imaging evaluation group. High-precision medical imaging techniques (e.g., CT, MRI) were employed to create digital 3D models, which were then converted into physical entities using 3D printing for surgical planning and simulation.ResultsBoth the 3D visualization group and the 3D visualization plus 3D printing group demonstrated superior outcomes in terms of surgery duration and blood loss compared to the traditional 2D CT group, indicating the efficacy of 3D reconstruction and 3D printing in preoperative planning. Postoperative recovery indicators, such as hospital stay and time to first flatus, were also more favorable in the groups utilizing 3D technology. Although there were no significant differences in postoperative complications and recurrence rates among the three groups, the groups using 3D technology showed advantages in reducing certain complications.ConclusionsThe results indicate that medical 3D technology has significant value in the surgical planning of advanced ovarian cancer, enhancing surgical precision and reducing intraoperative risks, which may aid in improving postoperative recovery.

This paper presents experimental evidence regarding a novel switchable dual-wavelength thulium-doped fiber laser (TDFL). Wavelength switching is achieved by combining a polarization-maintaining fiber Bragg grating (PM-FBG) with a polarization controller (PC). The three-coupler double-ring compound cavity (TC-DRC) structure, acting as a mode-selection filter, is designed to select a single longitudinal mode (SLM) from the dense longitudinal modes. This paper introduces the design and fabrication method of the TC-DRC filter and analyzes, in detail, the mechanism for SLM selection. The experimental results demonstrate that the designed filter exhibits excellent performance. By adjusting the PC, the TDFL achieves stable SLM operation at the wavelengths of 1940.54 nm and 1941.06 nm, respectively. The optical signal-to-noise ratio (OSNR) is superior to 65 dB. When the TDFL is tested at room temperature, there is no significant wavelength drift, and power fluctuations are less than 1.5 dB. The operation of the SLM is verified through the self-heterodyne method, and the laser maintains stable SLM states for both wavelengths after continuous operation for an hour. Furthermore, based on the phase noise demodulation method, the linewidths of both wavelengths are measured to be less than 10 kHz at the integration time of 0.001 s.

A single-longitudinal-mode (SLM) thulium-doped fiber laser, based on an eye-shaped passive dual-ring filter, is designed and constructed. The eye-shaped passive compound cavity consisting of four couplers is used to increase the longitudinal mode spacing, and its performance is numerically analyzed in detail. A homemade uniform fiber Bragg grating serves as a wavelength selection device and a saturable absorber is used to further suppress the intense longitudinal mode competition in the laser cavity, ensuring the single-longitudinal-mode output. The experimental results demonstrate a laser output with a center wavelength of 2,049.85 nm and an optical signal-to-noise ratio of 63 dB. Moreover, the power fluctuation is less than 0.6 dB, and the center wavelength fluctuation is less than 0.03 nm over a continuous measurement period of 60 min, demonstrating an excellent stability. The laser linewidth is measured using an unbalanced Michelson interferometer and β-separation line method, resulting in a linewidth of 11.22 kHz.

A thulium-doped fiber laser (TDFL) with switchable single-wavelength output was proposed and experimentally constructed, and its output characteristics were investigated. The central wavelengths were 1940.52 nm and 2048.04 nm, defined by a superimposed uniform fiber Bragg grating (SI-UFBG) with reflectivity larger than 92%. Switchable output was successfully achieved by using polarization-dependent loss, with the help of a drop-in polarization controller and an in-line polarizer. For both output wavelengths, optical signal-to-noise ratios larger than 80 dB were achieved. Maximum fluctuations of the central wavelengths of 1940.52 nm and 2048.02 nm under 60 min were, respectively, 0.04 nm and 0.01 nm. Maximum fluctuations of output power for the same wavelengths over the same time period were, respectively, 1.09 dB and 0.12 dB. Maximum output powers of 215.12 mW and 155.53 mW were achieved for the respective output wavelengths of 1940.52 nm and 2048.02 nm. Moreover, a tuning range of ∼2 nm was realized by enforcing a strain on the SI-UFBG. The proposed TDFL may be applied in laser medicine and free-space-related applications.

A switchable multi-wavelength thulium-doped fiber laser (TDFL) using either two-stage cascaded or two-segment Sagnac loop filters are proposed and analyzed. Both filters incorporate a 3-m and 1.7-m long polarization-maintaining fiber, which acts as a comb filter. By adjusting two polarization controllers, when the TDFL used a cascaded Sagnac loop filter, eight stable single-wavelength operations were obtained with easy switching among them. The wavelength range was 16.36 nm during the single-wavelength switchable operation, with the optical signal-to-noise ratio up to 55 dB. This TDFL can achieve at most quintuple-wavelength operation. When the TDFL used a two-segment Sagnac loop filter, we achieved single-wavelength and dual-wavelength switchable. This TDFL can achieve at most stable quadruple-wavelength operation. In dual-wavelength switchable operation, the maximum and minimum wavelength spacings were 21.78 nm and 1.50 nm. Due to its abundant range of wavelengths, the proposed TDFLs has great potential in wavelength-division multiplexing.

A high-power, narrow-linewidth, continuous-wave, thulium-doped fiber laser (TDFL) based on a master-oscillator power-amplifier (MOPA) was experimentally demonstrated. The main oscillator (seed source) yielded 0.64 W of narrow-linewidth laser output at a central wavelength of 1940.32 nm and a 3 dB spectral bandwidth of 0.05 nm. The output narrow-linewidth laser from the main oscillator was amplified by two-stage, cladding-pumped, thulium-doped, all-fiber amplifiers. The main amplifier yielded 26 W of narrow-linewidth laser at a central wavelength of 1940.33 nm. The slope efficiency of the main amplifier was approximately 55.6%. Significant residual pumping light component in the output laser was not observed. During the amplification process, no stimulated Brillouin scattering (SBS) effect, strong amplified spontaneous emission (ASE) effect, and parasitic lasers were observed at the reverse monitoring end. Moreover, the output power was only limited by the incident pump power and the output power had a good stability in a 50 min monitoring period.

We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber laser using two cascaded single-mode-four-mode-single-mode (SFS) fiber interferometers and a 150-m-long highly nonlinear fiber. The transmission properties of SFS fiber interferometers with two different four-mode fiber (FMF) lengths are analyzed theoretically. The interferometer with a longer FMF is used to select specific wavelengths, and the one with a shorter FMF is used to stimulate more laser lines. By adjusting the polarization controller and increasing the pump power, the number of output laser channels and the wavelength spacings can be changed and switched. By selecting the proper length of the FMFs, 31 lasing lines are achieved with covering a wavelength range of ~22 nm. The power fluctuation and the wavelength drift of the 31-wavelength operation for the proposed fiber laser are within 0.706 dB and 0.02 nm, respectively.

A wavelength-switchable single-longitudinal-mode thulium-doped fiber laser using a sampled fiber Bragg grating is proposed in this study. The laser can be switched between three single-wavelength and three dual-wavelength modes of operation. For the single-wavelength mode of operation, the maximum power and wavelength fluctuations in 50 min were ±0.404 dB and ±0.01 nm, and the linewidths at three wavelengths were 0.39, 1.88, and 0.89 kHz, respectively. For the dual-wavelength mode of operation, the maximum power and wavelength fluctuations in 20 min were ±0.926 dB and ±0.03 nm, respectively. The proposed thulium-doped fiber laser will find useful application in optical communication and free-space optical detection and sensing.

In this article, a precisely controlled, switchable thulium-doped fiber laser (TDFL) with high optical signal-to-noise ratio (OSNR) is proposed and demonstrated. A home-made multimode fiber Bragg grating (MMFBG) with multireflection peaks was used as an optical filter to select the desired lasing channel. Using a manually controlled fusion splicer, the axial misalignment was applied between the single mode fiber and the MMFBG to switch the output wavelength. In the experiment, the number of switchable lasing lines was up to 12, and the fluctuation of the center wavelength and output power was less than 0.03 nm and 0.67 dB, respectively. A maximum slope efficiency of 1.3% was obtained when the axial misalignment was 0 μm, and the OSNR was higher than 65 dB. In addition, the proposed fiber laser was used as an optical fiber laser sensor to quantify the strain applied on the MMFBG, and a sensitivity of 1.16 pm/μϵ was obtained.

A switchable multi-wavelength thulium-doped fiber laser (TDFL) using a four-mode fiber based Sagnac loop filter was proposed and demonstrated. The Sagnac loop, incorporating a 4.8 m long four-mode step-index fiber, acting as a comb filter was analyzed theoretically and experimentally. By adjusting two polarization controllers, eight stable single-wavelength operations and five stable dual-wavelength operations were obtained with easy switching between the different operation modes. The wavelength range covered during the single-wavelength switchable operation with a signal-to-noise ratio of up to 55 dB was ~28.51 nm. In dual-wavelength switchable operation, the maximum and minimum wavelength spacings were ~21.78 nm and ~1.50 nm, respectively. Due to the abundant wavelength resources, the proposed TDFL has great potential in wavelength division multiplexing free-space optical communications, optical fiber sensing, and photonic generation of microwave signals.

This paper proposes and demonstrates a single-longitudinal-mode thulium-doped fiber laser using a passive triple-coupler ring-based compound-cavity filter (TCR-CC) and a uniform fiber Bragg grating. For the first time, the TCR-CC filter is used to select a single mode from dense longitudinal modes. Experimental results show that laser in the wavelength of 1941.28 nm can maintain exceptional stability with an optical signal-to-noise ratio of 74.1 dB. The measured maximum wavelength drift and power fluctuation are 0.01 nm and 0.45 dB, respectively. Meanwhile, the measured linewidth of the laser is 910 Hz, and the relative intensity noise is below −125.82 dB/Hz above 2 MHz frequencies.

A continuous wave, switchable multi-wavelength, thulium-doped fiber laser (TDFL) with a polarization-maintaining sampled fiber Bragg grating (PM-SFBG) is proposed and demonstrated for the first time. A length of 150 m highly-nonlinear fiber (HNLF) was used to introduce the four-wave mixing effect for the efficient suppression of the wavelength competition existing in the gain medium of thulium-doped fiber. By adjusting the state of polarization (SOP) of light in the laser cavity, two six-wavelength operations at two orthogonal SOPs and a ten-wavelength operation were obtained. When the TDFL ran at the six-wavelength operation mode with a pump power of 4.11 W, there were at least four lasing wavelengths with an optical signal-to-noise ratio (OSNR) higher than 30 dB, and when it ran at the ten-wavelength operation mode with a pump power of 4.60 W, there were nine lasing wavelengths with an OSNR higher than 30 dB. Regardless of the operation mode, the TDFL exhibited high stability.