mW Laser Power Research Articles

Simultaneous transmission/absorption photometry of particle-laden filters from wildland fires during the Biomass Burning Observation Project (BBOP) field campaign

Transmissivity and absorptivity measurements were carried out simultaneously in the visible (wavelength of 532 nm) at laboratory conditions using particle-laden filters obtained from a three-wavelength particle/soot absorption photometer (PSAP). The particles were collected on filters from wildland fires over the Pacific Northwest during the Department of Energy Biomass Burning Observation Project (BBOP) field campaign in 2013. The objective of this investigation was to apply this measurement approach, referred to as simultaneous transmission/absorption photometry (STAP), to estimate the aerosol extinction coefficient from actual field-campaign filter aerosol, and compare results with the PSAP. The STAP approach offers several advantages over the PSAP, including estimation of the extinction coefficient from temperature measurements (avoiding the complexities associated with filter reflectivity/scattering measurements), as well as determination of the filter optical properties and filter effects on particle absorption (resulting in particle absorption enhancement).The experimental arrangement included a laser probe beam impinging normal to the particle-coated surface of a vertically mounted filter, and a thermocouple placed flush in the middle of (and in thermal contact with) the filter uncoated back surface. With this simple arrangement, the transmissivity and absorptivity were determined simultaneously at a given laser beam wavelength. The measurement repeatability was better than 0.3 K (95% confidence level) for temperature and 0.4 mW for laser power. The limit of detection for the extinction coefficient was estimated to be (8–12) Mm−1 (95% confidence level) at about 1.9 mW laser power. The extinction coefficient was determined through measurement of both PSAP blank and exposed filters. Filters were obtained from nine different aircraft flights conducted during the BBOP campaign, representing different flight patterns, days, stages of burning, landscapes, and wildland fires. The STAP extinction coefficient matched the darkness of the filter coating, however the PSAP-filter results did not follow the same order. Although there were differences in transmissivity between the two techniques, the estimated values for absorption coefficient were in good agreement.

Stability evaluation of water droplets levitated by a TinyLev acoustic levitator for laser induced breakdown spectroscopy

Stability of acoustic levitated water droplets, for laser induced breakdown spectroscopy (LIBS), is required in order to obtain shot-to-shot reproducibility and low limits of detection. Although stabilization is possible by increasing the TinyLev levitator's operational voltage, at high voltages liquid droplets shatter when inserted at the nodes of the acoustic levitator. An alternative for stabilization, it is the use of a four beam laser arrangement, similar to an optical trap. In this case, we have found adequate not to use focusing lenses, since the goal is just to exert certain lateral pressure to counteract the lateral pressure instabilities generated by the acoustic levitator and simplify the optical arrangement. For an operational voltage of 8.5 V, a reduction on the droplet's horizontal deviation of 42% is attained at 650 mW laser power. At these experimental conditions, LIBS measurements were conducted on water samples doped with different metals. It is shown that, at this droplet's deviation, it is possible to analyze liquid samples despite a complete liquid evaporation is not reached. For Al samples a limit of detection (LoD) of 0.22 ppm is calculated from a calibration curve, and LoD of 1.18, 0.15, 0.94 and 0.7 ppm for Cu, Mn, Pb and Ni respectively, are estimated by signal to noise ratios values. These results show that even though, the final size of the liquid droplets is large, there is not a reduction on the lowest detectable concentration obtained, compared to other LIBS works on liquid samples. Leading up to conclude that pre-concentration effect takes more relevance than residual liquid's detrimental effect.

Superficial photothermal laser ablation of ex vivo sheep esophagus using a cone-shaped optical fiber tip.

Superficial photothermal laser ablation (SPLA) may be useful as a therapeutic approach producing a depth of injury that is sufficient to eliminate mucosal lesion but not deep enough to induce thermal effects in deeper tissue layers. The purpose of this preliminary study is twofold: (a) to describe design steps of a fiber probe capable of delivering a tightly focused laser beam, including Monte-Carlo-based simulations, and (b) to complete the initial testing of the probe in a sheep esophagus model, ex vivo. The cone-shaped (tapered) fiber tip was obtained by chemical etching of the optical fiber. A 1505 nm diode laser providing power up to 500 mW was operated in continuous wave. The successful SPLA of the sheep mucosa layer was demonstrated for various speed-power combinations, including 300 mW laser power at a surface scanning rate of 0.5 mm/s and 450 mW laser power at a surface scanning rate of 2.0 mm/s. Upon further development, this probe may be useful for endoscopic photothermal laser ablation of the mucosa layer using relatively low laser power.

Raman scattering obtained from laser excitation of MAPbI3 single crystal

Finding renewable energy sources is of paramount importance to meet the increasing global energy demand whilst minimizing the impact on the environment. The research community has focused on solar energy as it is endlessly available, and have ranked the methylammonium lead iodide (MAPbI3) as one of the most promising candidate amongst perovskite solar cells. Despite its high efficiency, the MAPbI3 is sensitive to humidity, light, and temperature, its instability affects primarily on the crystalline structure and eventually leads to degradation. Three crystalline structures are known for this material, orthorhombic, tetragonal, and cubic which exist in different temperatures. Here we report on several processes detected from laser excitation of MAPbI3 single crystal at ambient conditions. A phase transition from tetragonal to cubic phase was induced by excitation of over 15 mW laser power. The phases were characterized by LF-Raman and photoluminescence, taken simultaneously with the increase of exciting laser power and the spectral changes were assigned to the structural differences. In addition, Raman stimulation of iodine vapors signal was observed, those vapors were generated from the core of the focus wherein the highest temperature led to degradation. The stimulated Raman phenomenon was enabled due to the unique properties of the MAPbI3 single crystal and revealed viability to use this material for additional applications in other research fields.

Initial dynamic thermal dissipation modes enhance heat dissipation in gold nanoparticle\u2013polydimethylsiloxane thin films

Plasmonic nanocomposite materials have exhibited value for applications ranging from biological hyperthermia to optical sensing and waveguiding. Energy absorbed from incident irradiation can be re-emitted as light or decay into phonons that propagate through the surrounding material and increase its temperature. Previous works have examined steady-state thermal dissipation resulting from irradiated plasmonic nanocomposites. This work shows heat dissipation in the first few seconds can significantly exceed that during subsequent steady state, depending on film geometry, nanoparticle diameter and concentration, laser irradiation power, and position within and adjacent to the irradiated spot. Films of lower thickness containing 16 nm gold nanoparticles (AuNPs) irradiated at 13.5 mW laser power showed highest enhancement and tunability of the dynamic thermal mode within and adjacent to the irradiated spot. Measured initial nanocomposite film temperature in or near the irradiated spot exceeded that resulting from constant bulk film thermal dissipation. These results improve understanding of cooling dynamics of resonantly irradiated nanocomposite materials and guide development of devices with enhanced thermal dissipation dynamics.

Microscopic research on the properties of optothermal microactuators with different lever ratios.

This paper presents microscopic research on properties of asymmetric optothermal microactuator (OTMA) with different lever ratios. A theoretical model is established on the basis of thermal flux theorem to describe the increase in temperature induced by laser irradiation and thermal expansion of OTMAs' expansion arms. The increases in temperature of three asymmetric OTMAs with total lengths/lever ratios of 540 μm/7.2, 1,080 μm/7.2, 1,080 μm/14.4 were simulated under irradiation of 2.8 mW laser beam, which revealed that a similar increase in temperature will distribute on three expansion arms, with maximum the temperature increase of 82.73, 87.67, and 88.03°C, respectively. Due to these increases in temperature, the arms expand longitudinally and thus the OTMAs are capable of deflecting laterally with enlarged deflection amplitudes. To obtain optimized deflecting properties, three OTMAs with aforementioned lever ratios are further microfabricated and experimented using an optical microscopic observation and measuring system combined with a charge-coupled device. The experimental results show that these OTMAs can be directly actuated by laser beam and acquire maximum deflections of 6.8, 7.2, and 11.4 μm when only 2.8 mW laser power is employed. In addition, it is demonstrated that, although doubling the lever ratio of OTMA does not correspondingly generate twofold deflection, the deflection amplitude can significantly increase with the increase in the lever ratio. With their characteristic elegances, the OTMAs are expected to be practically applied in the micro-electromechanical system and the micro-opto-electromechanical system.

Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arrays Sensitized by P‐Doped C3N4 Quantum Dots

AbstractBulk g‐C3N4 is an earth‐abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P‐doping and size quantization are combined to synthesize highly fluorescent P‐doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase‐phase and rutile‐phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight‐driven water‐splitting and as photocatalysts for surface catalytic reactions. Square‐shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD‐STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD‐STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light‐driven transformation of 4‐nitrobenzenethiol (4‐NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.

Capacitive Characteristics of High-Speed Photovoltaic Converters at Combined Lighting

p–i–n GaAs photovoltaic converters of modulated laser radiation (810–830 nm) transferring both energy (laser power) and information signal were developed. The capacitance and frequency characteristics of the photovoltaic converters at a constant 0.2–1 W and variable 16 mW laser power were studied. The dependences of the heterostructures capacitance on the voltage at the p–i–n junction were obtained; it has been found out that the charge accumulated in the i-layer plays the dominant role. As a result, the decrease in the thickness of the undoped region improves the frequency characteristics. This paper shows that at the voltage in the DC circuit of 0.8 V and the laser power of 0.6 W, the efficiency of 39% can be achieved with the 450 MHz transmission band in case of the 20 mV AC signal amplitude at the load of 2.5 Ω. For the voltage in the DC circuit of 1 V in similar modes of continuous laser radiation, the efficiency was 48.6%, and the transmission band was 135 MHz. Increasing the laser power to 1 W reduced the efficiency by about 1% and the bandwidth by 30 MHz. The achieved characteristics of the studied photovoltaic converters would make it possible to use them for providing autonomous power supply for devices with low power consumption at the data rate of 100 Mbit/s and above.

Investigating the effect of gold nanoparticles on hydatid cyst protoscolices under low-power green laser irradiation.

Various scolicidal agents are applied for the destruction of protoscolices in cysts media. Undesirable complications of the scolicidal agents limit the techniques to treat the cyst disease. Therefore, new non-toxic scolicidal agents are needed. Upon laser light irradiation, the photothermal gold nanoparticles (AuNPs) convert the absorbed laser light into heat through photothermal effect which kills the surrounding protoscolices by rising the temperature of the cysts media. In this study, we introduced biocompatible AuNPs as a non-toxic scolicidal agent to cure liver hydatid cysts. The protoscoleces were collected from the livers of naturally infected sheeps. In each experimental group, 1.5 mL suspensions of hydatid liquid containing protoscolices were added to test tubes. The test tubes were divided into five groups. Control, AuNPs only, Green laser only, High-dose AuNPs + laser and Low-dose AuNPs + laser groups. Two concentrations (0.4 and 0.8 mL) of AuNPs and three laser powers (30, 50, 150 mW) were applied for 30, 60 and 120 minutes to the groups. Then the ciysts liquid assessed under a light microscope and determined the viability of protoscoleces. Protoscolices in high-dose AuNPs group were destructed up to 89.30% deaths under 150 mW laser power for 120 minutes. However, negligible cell deaths were observed in cases where only AuNPs added or only laser irradiated groups. Increasing the dose of AuNPs or laser power or duration of aplication increased the protoscolosidal death rate. In the study, we have successfully demonstrated that the AuNPs are an effective therapeutic and scolicidal agent to cure hydatid cyst disease under laser irradiation.

Design and fabrication of optical waveguide as directional coupler using laser cutting CO2 on acrylic substrate

CO2 laser cutting machine can provide convenience on making various souvenirs and decorations and billboards. CO2 Laser cutting machines are widely used for cutting and grafting in some materials such as polymer, glass, paper, fabric and some non metallic materials. In this study using CO2 laser cutting to create a directional coupler channel. In the process of making the canal done with engraving on acrylic substrate with 4.2 mW laser power and speed 10 mm/seconds and then repeated three times. Directional coupler fabrication is done variation of interaction length 20 mm, 25 mm, 30 mm, 35 mm and 40 mm. The result of directional coupler fabrication resulted in a coupling ratio of 49.8: 50.2 at 25 mm interaction length with input A2. Directional coupler fabrication with CO2 laser cutting machine provides easy interaction length setting as it can be made with the engine and the results are in accordance with the desired design.

Flow-Induced Transport via Optical Heating of a Single Gold Nanoparticle

Optothermal trapping has gained increasing popularity in manipulation such as selecting, guiding, and positioning submicron objects because of a few mW laser power much lower than that required for optical trapping. The optotothermal trapping uses thermal gradient-induced phoretic motions, but the underlying physics of driving force has not been fully understood. In this study, we performed optotothermal trapping of 500-nm-diameter colloidal silica via a continuous laser illumination of a single gold nanoparticle from the bottom in a closed chamber. Under illumination, the tracer particles were attracted to the gold nanoparticle and trapped. Notably, the direction of migrating particles was always to hot gold nanoparticle regardless of the configuration of gold nanoparticle placed at two opposite sides of the chamber, on the bottom surface of an upper substrate (ceiling) or on the top surface of a lower substrate (floor). The previous interpretation based on thermal convective flow from the bottom to the top and circulating inside the chamber was only applicable to floor configuration and failed to explain our observation for ceiling. Instead, temperature-induced Marangoni effect at the water/superheated water interface is likely to play a role. This study promoted a better understanding of the driving mechanism in optothermal trapping. Moreover, as an application of the single-particle platform, we showed the photothermal phase separation-induced microdroplet formation of thermoresponsive polymers and the coating of non-thermoresponsive polymers on nanoparticles.

Thermal Lens Study of NIR Femtosecond Laser-Induced Convection in Alcohols.

We use time-resolved thermal lens (TL) experiments to examine the convective heat transfer at microscale in the first eight members of the homologous series of primary alcohols. TL measurements enable a direct study of these primary alcohols without adding any chromophore as a function of varying heat loads created via femtosecond laser pulses at 1560 nm. Convective heat transfer leads to the asymmetrical and reduced thermal gradient, which substantially weakens the TL signal. The inflection in the time profile of the TL signal of methanol at higher powers is attributed to the greater molecular convection in methanol compared to other samples. This inflection dies out with a decrease in laser power. Our results demonstrate that the convection is more prominent at higher laser powers in all samples, and it modifies the trend in the steady-state TL signal of different alcohols with pump laser power. Methanol also has the highest steady-state TL among the primary alcohol series at low laser powers. The maxima in the TL signal are shifted systematically from methanol to ethanol and then to propanol as the laser power increases. Semiempirical analysis of time-resolved TL signal by using the latest theoretical TL model enabled us to extract the coefficient of convective heat transfer in methanol at different laser powers. In addition to that, analysis of other members of alcohol series at the highest (7.3 mW) laser power shows that convection is more facile in short-chain alcohols compared to the long-chain alcohols.

Discrimination of non-melanoma skin cancer and keratosis from normal skin tissue in vivo and ex vivo by Raman spectroscopy

This study aimed the diagnosis of non-melanoma skin cancer (basal cell carcinoma - BCC, squamous cell carcinoma - SCC) and actinic keratosis (AK) and normal tissue (NO) by means of Raman spectra collected in vivo and ex vivo as well as determine, through the main Raman features, which biochemical element present in the skin is related to the spectral changes in the lesions compared to normal tissue. A total of 471 Raman spectra in vivo and 227 spectra ex vivo from NO, BCC, SCC and AK tissues were collected using a dispersive Raman spectrometer (830 nm excitation, 30 s exposure time, 200 mW laser power) as well as spectra of basal skin constituents (proteins, lipids, nucleic acids). Student's t-test (p < 0.01) was applied to identify the Raman peaks with significant differences of lesion compared to normal skin and discriminant analysis based on Euclidian and Mahalanobis distances were applied to the intensities of the significant peaks. The results showed better discrimination between lesions and normal tissue through Mahalanobis distance both in vivo and ex vivo, with sensitivity, specificity and overall accuracy of 94.1%, 93.6% and 93.8%, respectively, for the in vivo spectra, while the discrimination showed sensitivity, specificity and overall accuracy of 100% for ex vivo tissues. The use of the intensities of the significant Raman peaks in the discrimination model showed results compared to other multivariate methods and may allow faster processing time, increasing the possibility of clinical use.

Solvent‐Limited Ion‐Coupled Electron Transfer and Monolayer Thiol Stability in Au144 Cluster Films

AbstractVoltammetric investigations were carried out for Au144 cluster films protected by 1‐hexanethiol (C6S) and 2‐phenylethanethiol (PET) in acetonitrile (0.1 M TBAPF6) and in water (0.1 M KPF6). The C6S‐protected Au144 cluster films show single electron charging behavior both in acetonitrile and water electrolyte systems. Whereas, the PET‐protected Au144 cluster films show charging behavior only in acetonitrile and not in water, although both electrolyte systems contain a common hydrophobic anion (PF6−). This discrepancy is attributed to solvent‐limited ion‐coupled electron‐transfer phenomena. Furthermore, spectroelectrochemistry was employed to study the thermal and electrochemical stability of PET on curved/3D (Au144 cluster films) and flat/2D (self‐assembled monolayers (SAMs) of PET on a polycrystalline planar Au electrode) Au surfaces. At 4 mW laser power, the SAMs of the curved system remained stable; however, in the flat system, they irreversibly desorb from the surface. This was ascribed to the relative stability differences of the PET monolayer originating from the existence of different Au−S structures on the two types of Au surfaces.

Rapid and high-performance processing technology for large-area frequency selective surfaces

Frequency selective surfaces (FSSs) with periodic smart structures have widespread applications in many areas, especially in electromagnetic wave filters. In this paper, a rapid and high-performance processing technology for large-area FSSs was presented. This novel technology combined laser direct writing lithography (LDWL) with wet chemical etching (WCE) (i.e., LDWL + WCE). Basing on experiments and in the condition of optimal parameters (i.e., 40 mW laser power, 1000 mm/s scan speed, single scan, 20 μm hatch space, pattern-profile scan path, and ferric chloride aqueous solution as etchant) of LDWL + WCE, a large-area (200 × 200 mm2) aperture type FSS with 625 square-loop units was fabricated within 8 min on a FR-4 copper-clad plate (with 12 μm-thickness copper layer). When the same FSS was prepared by commonly-used laser direct ablation (LDA) technology with itself optimal processing parameters, it needed about 62 min (nearly 8 times as much time as the former). Scanning electron microscopy (SEM) and surface probe profilometry analyses showed that the edges of the square-loop patterns fabricated by LDWL + WCE were steeper and smoother, and the FR-4 substrate had no damage. In an anechoic chamber, the electromagnetic wave filtering performances of the as-prepared FSSs were tested, and the results indicated that the FSS fabricated by LDWL + WCE had a bandpass response at 7.08 GHz with a transmittance of 97.75%. Its frequency response curve was in better agreement with the simulation result. The technology of LDWL + WCE also has the potential to rapidly fabricate large-area and/or non-planar FSSs with high performance.

Research on characteristics of symmetric optothermal microactuators.

This paper proposes and studies symmetric optothermal microactuators (OTMAs) which are directly controlled by a laser beam. Based on the principle of thermal flux, a theoretical model is established to describe the laser-induced temperature rises and optothermal expansions of the OTMAs' expansion arms. Temperature rise distributions of the arms with lengths of 590, 990, and 2260 μm are simulated separately, which reveals that, under 2 mW laser irradiation, the maximum temperature rises are invariably less than 75.9°C. Simulations are also made to consider optothermal expansions of the arms caused by laser irradiation, which turns out that expansion increases considerably when the arm's length increases from 250 to 1000 μm, while insignificantly between 1250 and 2500 μm. Under a laser beam of 2 mW power, experiments on three microfabricated OTMAs have been further conducted, which demonstrate that the OTMAs are capable of generating maximum deflections of 7.3, 11.3, and 13.6 μm, and that the growth of deflection is comparatively obvious in the case when the total length changes from 750 to 1200 μm, while insignificant for the range between 1200 and 2380 μm. With regard to simulations and experiments, it has been proved that the OTMAs are capable of implementing direct laser-controlled microactuation in which only about 2 mW laser power is demanded. Moreover, it has been proved that twofold total length or arm length does not correspondingly result in doubling the deflection, nor the expansion. Therefore, total length/expansion arm's length around or less than 1200/1000 μm is more appropriate for obtaining satisfactory characteristics of OTMAs, which may be potentially applied in MEMS/MOEMS and micro-/nano-technology.

1550-nm Driven ErAs:In(Al)GaAs Photoconductor-Based Terahertz Time Domain System with 6.5 THz Bandwidth

ErAs:In(Al)GaAs superlattice photoconductors are grown using molecular beam epitaxy (MBE) with excellent material characteristics for terahertz time-domain spectroscopy (TDS) systems operating at 1550 nm. The transmitter material (Tx) features a record resistivity of 3.85 kΩcm and record breakdown field strength of 170 ± 40 kV/cm (dark) and 130 ± 20 kV/cm (illuminated with 45 mW laser power). Receivers (Rx) with different superlattice structures were fabricated showing very high mobility (775 cm2/Vs). The TDS system using these photoconductors features a bandwidth larger than 6.5 THz with a laser power of 45 mW at Tx and 16 mW at Rx.

Energy Transfer Mechanisms and Optical Thermometry of BaMgF4:Yb3+,Er3+ Phosphor.

Motivated from our previous studies on the upconversion properties of BaMgF4:Yb3+,Tb3+ phosphor, here we investigated the upconversion properties of BaMgF4:Yb3+,Er3+ phosphor. We demonstrate a two-way versatile approach for the fine-tuning of emission from green to the red region, by varying the dopant concentration and adjusting the pulse width of an infrared laser. The mechanism involved in tuning the emission color by laser power and pulse width variation was illustrated in detail. The temperature dependent upconversion spectra were studied by analyzing the fluorescence intensity ratio of the thermally coupled levels. The maximum sensitivity obtained is 83.29 × 10-4 K-1 at 583 K, which is much higher than the temperature sensitivity reported for other fluoride based materials. Moreover, the influence of the excitation power density on the ability of the phosphor for temperature sensing was also investigated. We obtained a maximum (∼415 K) temperature detection at 2563 mW laser power. The obtained results illustrate the potential use of BaMgF4:Yb3+,Er3+ phosphor in an optical thermometer due to its highly sensitive temperature detection ability.

Continuous-wave 1550 nm operated terahertz system using ErAs:In(Al)GaAs photo-conductors with 52 dB dynamic range at 1 THz

Telecom-wavelength compatible photoconductors benefit strongly from the large amount and affordability of telecom lasers and components but there are demanding requirements on material development. We demonstrate continuous-wave (CW) photomixing with a setup that only uses ErAs:In(Al)GaAs devices with a peak dynamic range (DNR) of 78 dB and a bandwidth of ∼3.65 THz at an integration time of 300 ms and only 26 mW laser power on each device. The ErAs:InGaAs receiver further features a factor of two lower noise equivalent power (NEP) than a state-of-the-art photoconductor, despite an antenna mismatch.

Dynamic properties of symmetric optothermal microactuator

This paper proposes a method of a symmetric optothermal microactuator (S-OTMA) directly driven by laser pulse. Based on the principle of thermal flux, a dynamic model is established describing the laser-induced optothermal temperature rise and optothermal expansion of the S-OTMA’s expansion arm. The dynamic optothermal expansion and the relationship between the expansion amplitude and laser pulse frequency are simulated, indicating that the expansion arm expands and reverts periodically with the same frequency of the laser pulse, and that the expansion amplitude decreases with the increase of laser pulse frequency. Experiments have been further conducted on a micro-fabricated S-OTMA under a laser pulse of 3.3 mW power and 2–18 Hz frequency. It is shown that the S-OTMA can periodically deflect in accordance with the same frequency of the laser pulse, with a maximum response frequency of at least 18 Hz. The maximum deflection (vibration) amplitude is measured to be 13.7 µm (at 2 Hz), and the amplitude decreases as the frequency increases. Both the theoretical model and experiments prove that the S-OTMA is capable of implementing direct laser-controlled microactuation in which only ~3 mW laser power is demanded. Furthermore, bi-directional actuation of the optothermal microactuator (such as S-OTMA) can be easily achieved by alternately irradiating either arm of the microactuator. This work may broaden the applications of the S-OTMA, as well as optothermal microactuators in MEMS/MOEMS and micro/nano-technology.