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Using a unique large-scale clickstream data set from a mobile commerce retailer, we examine the effect of the mobile shopping app and mobile operating system versions on consumer search and purchase behaviors in mobile commerce. We find that the consumers with an up-to-date shopping app or mobile operating system (but not both) compared to previous versions conduct more searches in terms of increased product page views and time spent on product pages, which in turn results in higher consumer purchase probability. Surprisingly, the consumers with both an up-to-date shopping app and mobile operating system have reduced search activities and lower purchase probabilities. Our results show that the mobile commerce environment affects the consumer shopping process in a non-linear fashion and indicate that there exists a "sweet spot" with the right level of smoothness in the mobile shopping environment. Our computations show that when compared to the baseline of using previous versions of both, using an up-to-date mobile shopping app alone increases consumer search activities by 336 more product pages or 1,975 more seconds spent, and using an up-to-date mobile operating system alone increases consumer search activities by 976 more product pages or 7,258 more seconds spent. However, using both an up-to-date mobile shopping app and mobile operating system only increases consumer search activities by 270 more product pages or 1,569 more seconds, compared to the baseline. One more product page viewed or one more second spent increases the average consumer purchase probability by 4.38% or 1.35%, respectively.

A challenge for online retail firms is managing stockouts when substitute products are available. Firms have options to set prices or offer substitute products to retain or release the consumers following stockouts. We develop a game-theoretic model in which competing online firms face the decision whether to price low enough so that, following product stockouts, their consumers remain in their stores by turning to unfamiliar substitute products that are in stock or even to attract their competitor’s consumers following stockouts at their competitor, or price high enough to release the consumers to the competitor. We demonstrate that our model’s unique equilibrium is one of three types: retain-consumer, release-consumer, or all-firm-i-consumer. Our analyses of the equilibria show that firms have the opportunity to use prices as a stockout recovery mechanisms, but surprisingly, they may choose not to do so under certain circumstances, dependent on the consumer search costs of unfamiliar substitute products on their sites.

Switchable metamaterial absorbers/reflectors (MAs/MRs) are important bifunctional electromagnetic devices and have been the subject of numerous scientific studies. However, there is a lack of bifunctional devices that operate in the terahertz band. Here, we theoretically propose a broadband switchable MA with many excellent properties, such as good thermal stability, high insensitivity to inferior film quality of the graphene, excitation polarization and wide incident angles, and outstanding structural parameter tolerance. The bandwidth of the proposed broadband MA is 3.4 THz with an absorptivity over 90% in the frequency band of 1.6-5 THz. The proposed absorber can switch to a reflector with a reflectivity over 93% by tuning the chemical potential of the graphene and reducing the temperature. Therefore, the switching intensity of the proposed MA exceeds 83%. The physical mechanisms of the broadband absorption of the proposed structure are investigated using the impedance matching theory and the multiple reflection interference theory. The reflection mechanism of the proposed broadband reflector is discussed by analyzing the effective parameters. The absorption and switching mechanism are theoretically investigated by performing detailed numerical calculations to analyze the surface loss intensity, electric field, and magnetic field. These findings can accelerate the development of terahertz broadband switchable devices.

A modified polarization-maintaining Sagnac loop mirror is proposed, and the simulated transmission spectrum of the proposed filter is in accordance with experimental transmission spectrum. Based on the proposed filter, a multi-wavelength thulium-doped fiber laser is constructed and experimentally demonstrated. The stable multi-wavelength oscillation within 60 minutes is achieved through the nonlinear polarization rotation effect enhanced by the highly nonlinear fiber. By fine tuning the polarization state, up to 35 lasing lines are obtained within a 10-dB bandwidth with wavelength separation of ∼1.38 nm at room temperature. The wavelength shift and the output power fluctuation are less than 0.04 nm and 1.69 dB, respectively. In addition, by changing the optical coupling ratio in the Sagnac loop mirror, different outputs with 7, 8, 16 lasing lines are also obtained.

A novel real-time interrogation technique based on an SMF-TMF-SMF (STS) structure and wavelength-to-time (WTT) mapping is proposed and experimentally demonstrated. An ultrashort optical pulse is first spectrally shaped by the homemade STS comb filter, which is formed by inserting a section of two-mode fiber (TMF) into single-mode fibers (SMF) using core-offset splicing. Linear WTT mapping is realized by employing a dispersive element and the spectrally-shaped waveform is mapped to the time domain. By monitoring the strain-encoded time shift, an ultrafast strain interrogation system with a measurement speed of 100 MHz and a strain sensitivity of 0.3 ps/ $\mu \varepsilon $ is obtained.

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.

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 $\sim 22$ 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 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.

The resonances with narrow linewidths generated in metamaterials are valuable for numerous applications ranging from bio-sensing to narrow-band filter. And breaking structural symmetry of metamaterials is one of the common and efficient approaches to achieve such sharp resonances. In this paper, we present symmetry breaking introduced in vertical split ring resonators (VSRR) metamaterials to excite narrow resonance. Different from the previously reported planar asymmetric metamaterials, the three-dimensional metamaterials are dominantly excited by the magnetic field component of the terahertz illumination together with the electric component. In this case, sharp resonances with characteristic magnetic field distributions are excited. And the sharpest resonance shows up with an ultra-narrow line-width (full width at half maximum, FWHM is 5.90 GHz) and high Q of 327 at 1.93 THz. Through systematic theoretical analysis and numerical mode implementation, we reveal the sharp resonance dips are produced by resonance hybridization between a resonance mode induced by the destruction of the structural symmetry and another special resonance inherent in the symmetric VSRR metamaterials. In addition, the fabrication robustness and sensing potential of the asymmetric VSRR metamaterials are explored in this paper. The results show that the AVSRR design is insensitive to the errors in the fabrication process, like rough metal surface and smooth metal corner, but highly sensitive to the approaching substance, which prove the excellent sensing performance.

Water table decline is one of the most serious environmental problems in the peatland in the Qinghai-Tibetan Plateau. However, the effect of water table decline on the structure of aboveground arthropod communities is still not clear. We investigated changes in the abundance of different arthropod groups, and estimated the abundance, height, and biomass of the plant community in a soil water table reduction experiment to reveal the effect of water table decline on the arthropod community structure. The effect of water level decline on herbivorous arthropods varied according to the feeding habits. Specifically, water table decline treatment decreased the abundance of grass-preferring herbivores but increased the abundance of forb-preferring herbivores. However, the density of predators (e.g., spiders) did not change significantly. The variations in arthropod communities were correlated with the increase in forbs and leaf nitrogen content in the water table decline treatments. Our experiment demonstrated that the effect of water table decline on plant communities cascades upwardly to alter the arthropod community. Such trophic interactions should be considered in studies aimed at predicting shifts in the arthropods communities in a changing climate.

Environmental DNA (eDNA) is a novel, non-invasive sampling procedure that allows the obtaining of genetic material directly from environmental samples without any evidence of biological sources. The eDNA methodology can greatly benefit from coupling it to reliable, portable and cost-effective tools able to perform decentralized measurements directly at the site of need and in resource-limited settings. Herein, we report a simple method for the selective analysis of eDNA using a magneto-assay with electrochemical detection. The proposed method involves the polymerase chain-reaction (PCR) amplification of mitochondrial eDNA of parasitic Salmon lice (Lepeophtheirus salmonis), extracted from seawater samples. The eDNA sequence was targeted via sandwich hybridization onto magnetic beads and enzymatic labeling was performed to obtain an electroactive product measured by differential pulse voltammetry. Quality by Design (QbD), a recent concept of science- and risk-oriented quality paradigm, was used for the optimization of the different parameters of the assay. Response surface methodology and Monte Carlo simulations were performed to define the method operable design region. The optimized electrochemical magneto-assay attained a limit of detection of 2.9 amol μL−1 of the short synthetic sea louse DNA analogue (43 bp). In addition, robustness testing using a further experimental design approach was performed for monitoring eDNA amplicons. Seawater samples spiked with individuals of free-swimming L. salmonis copepodite stages and seawater collected from tanks with sea lice-infested fish were analyzed.

A single longitudinal mode (SLM) fiber laser with a ring cavity based on Sagnac interferometer (SI) for temperature sensing in the 2-μm band is proposed and demonstrated. The simulation and experimental results show that the transmission spectrum of the SI filter is sensitive to temperature change. Based on this distinguishing feature, the correlation between the laser wavelength drift and temperature variation can be established. Experimental results show that the proposed laser operates stably at the resonant wavelength of 1988.21 nm and the optical signal-to-noise ratio is approximately 55 dB at ambient temperature. Through continuous measurement for 100 min, the fluctuation of the output laser power is lower than 0.74 dB, and the resonant wavelength shift is less than the minimum resolution of the spectrometer of 0.05 nm. This indicates that it has good stability for a certain period of time. At the same time, the laser operates stably in SLM state. A temperature sensitivity of 2.09 nm/°C is obtained in experiment. Notably, the proposed fiber laser sensor possesses the merits including high sensitivity, low cost and simple structure, which are beneficial to its practical application.

For the first time, to the best of the authors’ knowledge, the transmission characteristics of sampled fiber Bragg grating (SFBG) and phase-shifted SFBG (PS-SFBG) in the 2 μ m band were investigated theoretically and experimentally in detail. Using the transmission matrix method, the dependence of the transmission spectra of the SFBG and PS-SFBG on different grating parameters was simulated; the grade-zero bandwidths of the SFBG transmission peak and the PS-SFBG phase-shifted peak were as narrow as 0.076 and 0.022 nm respectively. Based on the theoretical analysis results, we experimentally fabricated the gratings with three narrow peaks. The results showed that the grade-0 transmission peak bandwidth of the SFBG and the phase-shifted-peak bandwidth of the PS-SFBG were narrower than 0.06 and 0.09 nm, respectively, indicating that the gratings are excellent filters for 2 μ m band multi-wavelength narrow-linewidth fiber lasers.

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.

Drug resistance and dose-limiting toxicities are significant barriers for treatment of multiple myeloma (MM). Bone marrow microenvironment (BMME) plays a major role in drug resistance in MM. Drug delivery with targeted nanoparticles have been shown to improve specificity and efficacy and reduce toxicity. We aim to improve treatments for MM by (1) using nanoparticle delivery to enhance efficacy and reduce toxicity; (2) targeting the tumor-associated endothelium for specific delivery of the cargo to the tumor area, and (3) synchronizing the delivery of chemotherapy (bortezomib; BTZ) and BMME-disrupting agents (ROCK inhibitor) to overcome BMME-induced drug resistance. We find that targeting the BMME with P-selectin glycoprotein ligand-1 (PSGL-1)-targeted BTZ and ROCK inhibitor-loaded liposomes is more effective than free drugs, non-targeted liposomes, and single-agent controls and reduces severe BTZ-associated side effects. These results support the use of PSGL-1-targeted multi-drug and even non-targeted liposomal BTZ formulations for the enhancement of patient outcome in MM., The tumour microenvironment (TME) has a major role in chemoresistance in multiple myeloma. The authors show that a nanoparticle targeted to TME and loaded with bortezomib (BTZ) and Y27632 is more effective than free drugs, non-targeted and single-agent controls and reduces BTZ-related side effects.

A broadband metamaterial absorber based on the novel design of the combination of cross and slotted-square graphene sheets is presented and analyzed from the perspectives: perfect absorptivity, absorption bandwidth, tunability and insensitivity.

Graphene plasmons have attracted great interest for constructing high-performance functional metamaterial devices, among which graphene-based narrowband metamaterial absorbers are valuable in numerous applications. In this paper, a graphene-dielectric-metal hybrid structure is proposed to achieve dual-band excellent absorption and high-performance refractive index sensing. Numerical simulations show that the designed structure exhibits a high Q factor of 277.8 at 1.945 THz, which is higher than most previously-reported results. The sensitivity of the proposed structure can be up to 1.84 THz/RIU when the analyte thickness is 80 μm, and it exhibits promise for sensing thin-film biomolecule and thick biologic tissues. The electromagnetic field distributions show that the electromagnetic energy is highly confined in the structure at the higher order plasmon resonance, which plays an important role in achieving the excellent characteristics of the proposed structure. The tunability of the proposed structure is realized via changing the gate voltage applied to the graphene and the angles of the incident THz wave. In addition, we reveal that the proposed structure can be switched between single-band, dual-band, and 3-band absorption by tuning the incident angle under TM and TE polarization. Further results demonstrate that the proposed device possesses good thermal stability, polarization insensitivity, and outstanding fabrication tolerance. We believe that the proposed dual-band narrowband absorber can serve as a good example for other devices based on plasmons, such as selective sensors, modulators, and optical detectors.

While the literature on comparing the online and offline markets from the supply-side perspective is extensive, fewer researches have focused on the demand-side. Using a large-scale point-of-sales (POS) dataset on consumer packaged goods, we estimate a structural demand model and conducted counterfactuals of the price change or product stockouts. Our key findings are: 1) the own-price elasticity of demand is higher offline (i.e., –1.74 on average) than online (i.e., –0.87 on average). 2) The cross-price elasticity is also higher offline (i.e., 0.17 on average) than online (i.e., 0.04 on average). 3) When a product is out-of-stock, a larger portion of the loss of the market share is recovered more in the common products in the offline markets than that in the online markets. Specifically, 6.55 % of the loss of the market share goes to common products offline on average, while 6.05 % of the loss of the market share goes to the common product online on average. Our further analyses show that, when considering substitute products, the impact of price increases is surprising. The retailer may not be worse off by increasing prices because the gains in the revenue from the substitute products can make up more than the losses. The manufacturers may lose revenue by increasing prices or product stockouts. However, consumers are hurt more in the offline markets following the price increases of the common products because the offline market is more concentrated on the common products.

A novel approach for ultrafast and temperature-insensitive strain interrogation using a polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac loop interferometer (SLI) and linear wavelength-to-time (WTT) mapping is proposed and experimentally demonstrated. The PM-PCF incorporated in the SLI is used as the sensing element to achieve stable strain sensing with ultra-low temperature-dependence due to its intrinsic thermal insensitivity, which can be used to eliminate the cross-sensitivity effect and increase the measurement accuracy. A dispersive element is employed to realize the WTT mapping and real-time strain interrogation is obtained by converting the strain-encoded wavelength shift to time shift in the temporal domain, which can be directly monitored by a real-time oscilloscope. The proposed system offers an ultrafast interrogation speed of 100 MHz and a strain sensitivity of -0.17 ps/με.

A compound-cavity-based six-wavelength-switchable single-longitudinal-mode (SLM) thulium-doped fiber laser (TDFL) with a homemade polarization-maintaining sampled fiber Bragg grating (PM-SFBG) is proposed and demonstrated. The PM-SFBG in the 2 μm band is studied theoretically and experimentally, and is utilized as a polarization-dependent multi-channel reflecting filter in a multi-wavelength-switchable fiber laser, both for the first time. The SLM lasing in each channel is guaranteed by using a tri-ring sub-cavity. 6 single-wavelength operations are easily obtained and switched each other, and the maximum power and wavelength fluctuations are as low as 0.71 dB and 0.02 nm, respectively. The frequency noise of each lasing wavelength is measured through an unbalanced Michelson interferometry system, and the linewidths for all six lasing wavelengths are among 0.60–1.08 kHz, calculated by the β-separation line method on the basis of the measured frequency noise spectra. Benefiting from the enhanced polarization hole burning effect formed in the gain fiber, 9 switchable dual-wavelength operations with different wavelength intervals and orthogonal polarizations at two lasing wavelengths are obtained with the maximum power and wavelength fluctuations of only 0.95 dB and 0.03 nm, respectively. We believe the proposed TDFL will find great applications as an ideal light source in free space optical communication and optical sensing.

Principles of single- and multi-phase-shifted chirped fiber Bragg grating (CFBG) in 2 μm band are analyzed with transmission matrix method, and transmission characteristics, including transmissivity, wavelength and bandwidth performance, of single- and multi-phase-shifted CFBG in 2 μm band with different grating parameters are discussed by simulation. It is found that phase-shifted position, grating length, chirped coefficient and refractive index modulation amplitude all have impacts on bandwidth of phase-shifted transmission peak. The transmission peak bandwidths of single-, dual- and tri-phase-shifted CFBG can reach to 0.0270, 0.0172 and 0.0112 nm respectively. The experiment of phase-shifted CFBG verifies the correctness of the simulation, and the bandwidths of 0.0901 and 0.0480 nm are acquired for single- and dual-phase-shifted CFBG respectively, which are narrower than previous filters based on fiber Bragg grating in 2 μm band multi-wavelength fiber laser system.

A switchable single-polarization (SP) dual-wavelength mode-locked thulium-doped fiber laser using the polarization maintaining fiber Bragg grating and semiconductor saturable absorber mirror is proposed in 2- $\mu \text{m}$ band. By adjusting the polarization controller, stable dual-wavelength pulse lasing operation and SP single-wavelength pulse lasing operation are obtained. The dual-wavelength pulse lasing operation is obtained at 1940.97 and 1941.73 nm. In the SP single-wavelength pulse lasing state, the polarization extinction ratios are higher than 30 dB, the SP pulse duration are 3.75 and 3.73 ps.

Introduction With the legalization of both medical and recreational marijuana in some countries and a few US states, its use has become more widely prevalent. Both exogenous cannabinoids such as tetrahydrocannabinol (THC) and endogenous cannabinoids (endocannabinoids) have been shown to affect female gonadotropin pathways and female sexuality. Yet, our understanding of the mechanisms and effects on female sexual function is limited. Aim To review the literature regarding the effects of both endogenous and exogenous cannabinoids on female sexual function in both animals and humans. Methods We performed a PubMed search for English-language articles in peer-reviewed journals between 1970 and 2019. We used the following search terms: “cannabinoids,” “endocannabinoids,” “marijuana,” “cannabis,” and “female sexual function” or “sexual function.” The main outcomes of the papers were reviewed. Main Outcome Measure The main outcome measure was sexual function in females. Results A total of 12 human studies and 8 animal studies that evaluated the relationship between cannabinoids and female sexual function were included. Study types in animals were blinded, prospective, placebo-controlled trials. Human studies were based primarily on questionnaire data. The data indicate dose-dependent effects on female sexual desire and receptivity, such that low doses generally facilitate or have no effect but high doses inhibit. Conclusions More research is needed to develop a better understanding of the effects of cannabinoids on female sexual function. There does appear to be an effect on both animals and humans, but whether the effect is positive or negative along dose and species lines requires more study. With the legalization of marijuana occurring in more countries and more US states, there needs to be more well-controlled studies evaluating the effects.

Soil respiration is one of the largest carbon (C) sources in terrestrial ecosystems and is sensitive to soil nutrient variation. Although nitrogen (N) availability affects soil respiration, other nutrients, such as phosphorous (P), which play pivotal roles in plant growth and microbial activity, may also affect soil respiration. In addition, N and P have been widely reported to interactively affect plant growth; however, their interactive effects on soil respiration have rarely been studied. Therefore, we conducted a short-term, two-factor experiment (from 2013 to 2015) to determine whether N and P addition can interactively affect soil respiration in a northern Chinese steppe. Nitrogen addition elevated soil respiration by 9.5%, whereas P addition did not affect soil respiration in the studied steppe across all treatments. However, neither N nor P addition significantly affected soil respiration alone in the experiment. Furthermore, N and P interactively affected soil respiration. Nitrogen addition did not affect soil respiration in the ambient P plots, but significantly elevated soil respiration (by 17.7%) in P addition plots across the three growing seasons. The effects of N addition on soil respiration were primarily correlated with the responses of vegetation cover and litter biomass to N addition in the experiment. Our results demonstrate that P addition augments the effects of N addition on soil respiration. Soil nutrient contents should be incorporated into predictive models for terrestrial C cycle response to N addition.

A switchable, thulium-doped, isolator-free fiber laser is proposed and demonstrated. The isolator-free configuration, wavelength selective element and stabilization mechanism were achieved by using a theta cavity design, a two-mode fiber filter and nonlinear polarization rotation, respectively. By properly adjusting the polarization controllers to induce polarization-dependent loss, single- and dual-wavelength outputs can be obtained, and the stability of single- and dual-wavelength operations was measured for 30 min in each case. The single wavelength can be switched from 1959.17 to 1994.86 nm in a lasing range of ~35.7 nm with an optical signal-to-noise ratio (OSNR) of up to ~60 dB. When lasing dual-wavelength, the wavelength interval can be changed from ~4 to 27.36 nm with an OSNR higher than 42 dB, and the maximal lasing range of the dual-wavelength is 23.38 nm. In addition, the wavelength drift and power fluctuation of the proposed fiber laser are less than 0.14 nm and 1.976 dB, respectively, at room temperature, which demonstrates that the thulium-doped fiber laser has favorable wavelength and power stability.

The emerging material of graphene has resulted in new options for the design of metamaterial devices with excellent performances, offering an attractive platform for electromagnetic absorption applications. To date, researches on patterned graphene-based metamaterial absorbers (MAs), have focused on achieving broadband absorption while maintaining many excellent properties. Here, we propose a broadband tunable MA with a perfect absorption based on a novel design of the combination of cross- and square-shaped graphene sheets. Numerical simulation results show that the bandwidth of the proposed broadband MA reaches 2.76 THz with the absorptivity greater than 90% for both the transverse electric (TE) and transverse magnetic (TM) modes, which exceeds most of broadband absorption results achieved by MAs in previous studies. A numerical analysis employing the equivalent circuit model for the designed structure is conducted to determine the influence of the structural parameters on the absorptivity and optimize the parameters. Results show that impedance matching is achieved between the input impedance and the free-space impedance at the absorption band. Detailed numerical simulations are conducted to calculate the surface loss density, electric field, and surface currents to obtain an understanding of the high absorption mechanism. Also, the designed MA exhibits excellent properties, such as tunability, polarization independence, incident angle insensitivity and outstanding tolerance to changes in the structural parameters, suggesting that the proposed absorber is a promising candidate for various applications in the terahertz band.

A switchable single-polarization (SP), dual-wavelength thulium-doped fiber laser using polarization maintaining (PM) Fabry–Perot (F–P) filter is proposed. A combination of the PM F–P filter, a polarization controller (PC) and a polarizer is used to ensure the SP lasing operation. A stable dual-wavelength lasing operation is obtained at 1941.82 nm and 1942.21 nm. By adjusting the PCs, the proposed laser can achieve SP single-wavelength lasing operation; the polarization extinction ratios are higher than 33 dB. When the pump power is higher than 2.98 W, the optical signal-to-noise ratios of the SP single-wavelength operation can reach 60 dB, and the output power variations are less than 0.32 dB ( X -polarization) and 0.30 dB ( Y -polarization). The slope efficiencies of SP lasing operation are 6.26% ( X -polarization) and 8.79% ( Y -polarization), respectively.