Strong Saturation Research Articles

Stoichiometric dependent optical limiting in PLD SiOx thin films

In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiOx) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O2 pressure in the range of 5×10 -5 to 0.5 mbar. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O2 pressure. Raman spectra of SiOx films depicted the presence of micron sized clusters composed of nanocrystalline Silicon embedded in uniform matrix of oxidized amorphous Silicon. The open Z-scan of the thin films, under cw He-Ne laser irradiation, showed strong reverse saturation absorption (RSA) features and non linear absorption (NLA) coefficient, β, was found to be decreasing from 23.5 cm/W to 1.64 cm/W, with increase in O2 pressure from 5×10 -5 to 10 -1 mbar, respectively. Also, the SiOx films except that with maximum oxygen content showed optical limiting, where limiting threshold increases with increasing transparency controlled by oxygen content. The key feature of the present work is the tunability in linear absorption, nonlinear RSA and optical limiting in the SiOx films which can be used as novel material for optical switching application.

Stoichiometry-dependent linear and nonlinear optical properties of PLD SiO x thin films

Abstract In this paper, the effect of oxygen content on the linear and nonlinear optical properties of the nanostructured SiO x thin films on fused silica is reported. The films were fabricated by Pulsed Laser Deposition technique at a substrate temperature of 400 °C in presence of O 2 pressure, ranging from 10 −4 to 0.5 mbar. X-Ray Diffraction spectra confirmed the formation of polycrystalline Si. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O 2 pressure. Linear absorption coefficients and refractive index were estimated from UV–Vis–NIR transmission spectra. Static refractive index of the films was found to vary from 3.57 to 1.57, with the increase in O 2 pressure. The open Z -scan spectrum of the thin films, using He-Ne laser, exhibited strong reverse saturation absorption and the non linear absorption coefficient measured from it was observed to be decreasing from 21.4 to 2.0 cm/W, with increase in the O 2 pressure. The closed aperture Z -scan of SiO x films depicted self-focusing property and the nonlinear refraction coefficient found to be decreasing from 44.2 × 10 −5 to1.9 × 10 −5 cm 2 /W, with increasing O 2 pressure. The significantly large nonlinear third order susceptibility of the order of 10 −1 –10 −3 esu was observed in these films. The SiO x films except the one containing maximum oxygen content exhibited optical limiting, where limiting threshold increases with increasing transparency which in turn is modulated by oxygen content.

Third-Order Nonlinear Optical Properties of InN Thin Films Under 532 nm Nanosecond Laser Pulses.

In order to investigate the third-order nonlinear optical properties of InN thin film, the sample was deposited on sapphire substrates by reactive RF magnetron sputtering. The prepared samples with a hexagonal wurtzite structure were confirmed by both X-ray diffraction (XRD) and scanning electron microscope (SEM). The optical absorption spectrum of the prepared samples was measured by a double beam UV/Visible spectrophotometer. The results show that the optical bandgap of deposited thin film is 2.06 eV. The third-order nonlinear optical coefficients of the film were measured by using the open and closed aperture transmission Z-scan (TZ-scan) technique under nanosecond laser pulses with a wavelength of 532 nm. The test results show that the prepared InN thin film performs strong saturation absorption, and the InN thin film with positive nonlinear refractive index coefficient is the self-focusing material under the conditions of the nanosecond laser pulses with the photon energy larger than the bandgap of prepared samples.

Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide.

Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAPTM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAPTM 5000 XS system.

Optimal single‐electron feedback control

AbstractIn a closed‐loop controlled single‐electron transistor (SET) the optimal feedback response is investigated, leading to a maximum suppression of shot‐noise. Using a coupled quantum point contact (QPC) charge detector, the tunneling process is monitored in real‐time and the fluctuations are fed back periodically to the tunneling barriers of the SET. The feedback response is applied proportional to the deviation from the target number of average transferred electrons. This leads to a strong suppression and temporal saturation of the cumulants of the full counting statistics. For the optimal feedback response, the saturation value of second cumulant is found to be given by target number. Astonishingly, the feedback works robust even for target numbers much smaller than one.

Hemoglobin S Exhibits Distinct MRI Oximetry Calibration in Vitro

Cerebral oxygen extraction fraction (OEF) is a powerful biomarker that could be used to stratify cerebrovascular morbidity in patients with sickle cell disease (SCD). Recently, several MRI intravascular oximetry techniques have demonstrated early feasibility in non-invasively quantitating OEF. Critical to this technique is the use of empirically derived calibrations that convert the measured magnetic relaxation property, T2, into oxygen saturation. Previous work demonstrated a strong hematocrit and saturation dependence on T2 and our prior work extended early results to hematocrit ranges common in patients with chronic anemia1. Despite improvements in calibration models, it remains an unanswered question whether the unique hemorheologic properties of hemoglobin S (HbS) containing red cells will give rise to fundamentally distinct magnetic properties compared to healthy, hemoglobin A (HbA) cells.Methods: All studies were performed on at CHLA under an IRB protocol with consent/assent. The blood of 11 subjects with sickle cell disease were studied (6 Male, 5 Female, aged 25.4 ± 14.5 years). Six had HbSS, three had HbSC, and two had HbSB0). Three of the subjects were on chronic transfusion therapy (2HbSS, 1 HbSB0). Two tablespoons of blood was drawn for the antecubital vein and stored at 4°C until analysis. For analysis, blood was placed in a custom built imaging apparatus and heated to 37° C. Oxygen level was measured with a hemoximeter and T2 was measured within a 3T Philips scanner. Following the T2 measurement blood was removed from the imaging apparatus and desaturated in a temperature controlled chamber using a membrane oxygenator and 5% CO2 and 95% N2 gas mixture. MRI T2 measurements and deoxygenation were repeated until a blood saturation level of ~30% was reached. T2 was measured with a phase cycled, CPMG sequence with 0, 4, 8 16 inversions pulse and a tau of 10ms. Monoexponetial fitting was used to derive T2.Results: Our previous work using a similar system and HbA blood demonstrated a highly reproducible relationship linking T2 to hematocrit and oxygen saturation (Y) as follows:R2= 1/T2 = A1*HCT*(1-Y)2 + A2*(1-Y)2 + A3*HCT + A4where the coefficients A1, A2, A3, and A4 were fit to data from a broad range of hematocrit and oxygen saturation values. In blood from sickle cell patients, we found that the A1 and A3 terms were zero. Thus the calibration curve was essentially independent of hematocrit. Figure 1 shows the tight relationship between hematocrit and 1/T2 for HbA could not be reproduced in HbS blood. In Figure 2, 1/T2 maintained a tight relationship (R2=.981) with (1-Y)2. The slope of 1/T2 and (1-Y)2was higher in HbS blood compared to HbA. There was also a positive relationship between HbS% and the residual of (1-Y)2 and R2 however this is was a weak effect (R2=0.057).Discussion: We found that the T2 of HbS containing red cells is distinct from the healthy HbA containing cells. This work has clinical implications for intravascular MRI oximetry performed in patients with sickle cell disease2 in that neglecting the magnetic differences between HbA and HbS may result in a 9.5%± 2.8% average bias in absolute saturation at a HCT of 32% . Interestingly, we were unable find a difference across sickle phenotypes and only small differences in transfused vs nontransfused patients. We suspect that irreversibly sickled cells, even few in number, will greatly influence the local magnetic field and shorten the T2 of sickle blood. It remains to be shown whether the in vitro conditions of this experiment are applicable to in vivo condition more broadly. In-vivo cross-validation studies are ongoing.1). Bush et al. MRM 20162). Jordan LC et al. Brain 2016Jordan LC, Gindville MC, Scott AO, et al. Non-invasive imaging of oxygen extraction fraction in adults with sickle cell anaemia. Brain2016;139(Pt 3):738-5 [Display omitted] [Display omitted] DisclosuresWood:World Care Clinical: Consultancy; Celgene: Consultancy; World Care Clinical: Consultancy; Vifor: Consultancy; Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Ionis Pharmaceuticals: Consultancy; Celgene: Consultancy; AMAG: Consultancy; AMAG: Consultancy; Apopharma: Consultancy; Apopharma: Consultancy; Biomed Informatics: Consultancy; Biomed Informatics: Consultancy.

Coherent backscattering of inelastic photons from atoms and their mirror images

Coherent backscattering is a coherence effect in the propagation of waves through disordered media involving two or more scattering events. Here, we report on the observation of coherent backscattering from individual atoms and their mirror images. This system displays two important advantages: First, the effect can be observed at low optical densities, which allows to work in very dilute clouds or far from resonance. Second, due to the fact that the radiation of an atom interferes constructively with that of its own image, the phenomenon is much more robust to dephasing induced by strong saturation. In particular, the contribution of inelastically scattered photons to the interference process is demonstrated.

ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole mass determination

We report the results of Swift/XRT observations (2008-2015) of a hyper-luminous X-ray source, ESO 243-49 HLX-1. We found a strong observational evidence that ESO 243-49 HLX-1 underwent spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of ESO 243-49 HLX-1 are well fitted by the so-{called} bulk motion Comptonization model for all spectral states. We have established the photon index Gamma saturation level, Gamma_{sat}$=3.0+/-0.1, in the correlation of Gamma versus mass accretion rate dot M. This Gamma-dot M correlation allows us to estimate the black hole (BH) mass in ESO 243-49 HLX-1 to be M_{BH}~ 7x 10^4 solar masses, assuming the distance to ESO 243-49 of 95 Mpc. For the BH mass estimate we used the scaling method, taking Galactic BHs XTE~J1550-564, H~1743-322 and 4U~1630-472, and an extragalactic BH source, M101 ULX-1 as reference sources. The Gamma-dot M correlation revealed in ESO 243-49 HLX-1 is similar to those in a number of Galactic and extragalactic BHs and it clearly shows the correlation along with the strong Gamma saturation at ~ 3. This is a reliable observational evidence of a BH in ESO 243-49 HLX-1. We also found that the seed (disk) photon temperatures are quite low, of order of 50-140 eV which are consistent with a high BH mass in ESO 243-49 HLX-1.

Self-consistent model for the saturation mechanism of the response to harmonic forcing in the backward-facing step flow

Certain flows denominated as amplifiers are characterized by their global linear stability while showing large linear amplifications to sustained perturbations. As the forcing amplitude increases, a strong saturation of the response appears when compared to the linear prediction. However, a predictive model that describes the saturation of the response to higher amplitudes of forcing in stable laminar flows is still missing. While an asymptotic analysis based on the weakly nonlinear theory shows qualitative agreement only for very small forcing amplitudes, the linear response to harmonic forcing around the mean flow computed by direct numerical simulations presents a good prediction of the saturation also at higher forcing amplitudes. These results suggest that the saturation process is governed by the Reynolds stress and thus motivate the introduction of a simple self-consistent model. The model consists of a decomposition of the full nonlinear Navier–Stokes equations in a mean flow equation together with a linear perturbation equation around the mean flow, which are coupled through the Reynolds stress. The full fluctuating response and the resulting Reynolds stress are approximated by the first harmonic calculated from the linear response to the forcing around the aforementioned mean flow. This closed set of coupled equations is solved in an iterative manner as partial nonlinearity is still preserved in the mean flow equation despite the assumed simplifications. The results show an accurate prediction of the response energy when compared to direct numerical simulations. The approximated coupling is strong enough to retain the main nonlinear effects of the saturation process. Hence, a simple physical picture is formalized, wherein the response modifies the mean flow through the Reynolds stress in such a way that the correct response energy is attained.

Fast response Antiwindup PI speed controller of Brushless DC motor drive: Modeling, simulation and implementation on DSP

Most of the Brushless DC (BLDC) motors drive adopts proportional, integral and derivative (PID) controller and pulse width modulation (PWM) scheme for speed control. Hence, BLDC motor drive has strong saturation characteristics. The saturation results in a typical windup phenomenon. The paper presents an Antiwindup drive for BLDC motor. An Antiwindup controller (AWC) has been used in the paper. AWC has been modeled in MATLAB/Simulink and comparison has been done between conventional PI controller and AWC at different starting loads. Dynamic characteristics of the BLDC motor drive have been examined and results are presented and discussed in detail in this paper. Details of DSP based experimental validation of the simulated results are also presented here.

Nonlinear Terahertz Absorption of Graphene Plasmons.

Subwavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, subwavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a terahertz pump-terahertz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by 2 orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results. The model shows that the observed strong linearity is caused by an unexpected red shift of plasmon resonance together with a broadening and weakening of the resonance caused by the transient increase in electron temperature. The model further predicts that even greater resonant enhancement of the nonlinear response can be expected in high-mobility graphene, suggesting that nonlinear graphene plasmonic devices could be promising candidates for nonlinear optical processing.

Adaptive Subdomain Model Order Reduction With Discrete Empirical Interpolation Method for Nonlinear Magneto-Quasi-Static Problems

This paper presents a novel adaptive subdomain model order reduction (MOR) based on proper orthogonal decomposition (POD) and discrete empirical interpolation (DEI) methods for nonlinear magneto-quasi-static (MQS) problems. In this method, a nonlinear region is decomposed into two regions, where one of the regions includes all those finite elements that have a particularly strong saturation and the other region does not. MOR based on POD and DEI methods is applied only to the latter region. Both the regions are determined automatically at each time step. It is shown that this method can effectively reduce the computational time to solve the nonlinear MQS problems without losing the quality of accuracy.

Asymmetrical Geometries in Electrical Machines

This paper describes and classifies possibilities of using asymmetric geometry solutions in slotted electrical machines with nonlinear soft magnetic core. These asymmetrical optimizations can reduce cogging torque and torque ripple at the nominal load. Additionally, some of them can improve overload capability, and field weakening capability by proper optimization of over-saturated regions of soft magnetic core. In this paper it is shown that the geometry of the soft magnetic core regions of TC-PMSMs, exhibiting strong saturation due to the interaction of PM- and armature reaction fluxes, has a significant impact on the torque quality. Therefore, by their modifications (including asymmetrical) it is possible to improve the machine characteristics. Two types of PMSM rotor arrangements (embedded-magnet rotor PMSM and rotor-surface magnet PMSM) were simulated with 2D FEM. The results showed that slight modification of the TC-PMSMs soft magnetic regions near by the air gap which exhibit the strongest saturation can lead to significant torque quality variation as well as to synchronous inductance changes.

Justification of the saturation assumption

The saturation assumption is widely used in computational science and engineering, usually without any rigorous theoretical justification and even despite of counterexamples for some coarse meshes known in the mathematical literature. On the other hand, there is overwhelming numerical evidence at least in an asymptotic regime for the validity of the saturation. In the generalized form, the assumption states, for any $$0<\varepsilon \le 1$$0<?≤1, that $$\begin{aligned} ||| u - {\hat{U}} |||^2 \le (1- \varepsilon /C) ||| u - U |||^2+ \varepsilon \mathrm{osc}^2(f,\mathcal {N}) \end{aligned}$$|||u-U^|||2≤(1-?/C)|||u-U|||2+?osc2(f,N)for the exact solution u and the first-order conforming finite element solution U (resp. $${\hat{U}}$$U^) of the Poisson model problem with respect to a regular triangulation $$\mathcal {T}$$T (resp. $${\hat{\mathcal {T}}}$$T^) and its uniform refinement $${\hat{\mathcal {T}}}$$T^ within the class $$\mathbb {T}$$T of admissible triangulations. The point is that the patch-oriented oscillations $$\mathrm{osc}(f,\mathcal {N})$$osc(f,N) vanish for constant right-hand sides $$f\equiv 1$$f?1 and may be of higher order for smooth f, while the strong reduction factor $$(1- \varepsilon /C)<1$$(1-?/C)<1 involves some universal constant C which exclusively depends on the set of admissible triangulations and so on the initial triangulation only. This paper proves the inequality (SA) for the energy norms of the errors for any admissible triangulation $$\mathcal {T}$$T in $$\mathbb {T}$$T up to computable pathological situations characterized by failing the weak saturation test (WS). This computational test (WS) for some triangulation $$\mathcal {T}$$T states that the solutions U and $${\hat{U}}$$U^ do not coincide for the constant right-hand side $$f\equiv 1$$f?1. The set of possible counterexamples is characterized as $$\mathcal {T}$$T with no interior node or exactly one interior node which is the vertex of all triangles and $${\hat{\mathcal {T}}}$$T^ is a particular uniform bisec3 refinement. In particular, the strong saturation assumption holds for all triangulations with more than one degree of freedom. The weak saturation test (WS) is only required for zero or one degree of freedom and gives a definite outcome with O(1) operations. The only counterexamples known so far are regular n-polygons. The paper also discusses a generalization to linear elliptic second-order PDEs with small convection to prove that saturation is somehow generic and fails only in very particular situations characterised by (WS).

Multi-Watt femtosecond optical parametric master oscillator power amplifier at 43 MHz.

We present a high repetition rate mid-infrared optical parametric master oscillator power amplifier (MOPA) scheme, which is tunable from 1370 to 4120nm. Up to 4.3W average output power are generated at 1370nm, corresponding to a photon conversion efficiency of 78%. Bandwidths of 6 to 12nm with pulse durations between 250 and 400fs have been measured. Strong conversion saturation over the whole signal range is observed, resulting in excellent power stability. The system consists of a fiber-feedback optical parametric oscillator that seeds an optical parametric power amplifier. Both systems are pumped by the same Yb:KGW femtosecond oscillator.

Flexible Graphene Field-Effect Transistors Encapsulated in Hexagonal Boron Nitride.

Flexible graphene field-effect transistors (GFETs) are fabricated with graphene channels fully encapsulated in hexagonal boron nitride (hBN) implementing a self-aligned fabrication scheme. Flexible GFETs fabricated with channel lengths of 2 μm demonstrate exceptional room-temperature carrier mobility (μFE = 10 000 cm(2) V(-1) s(-1)), strong current saturation characteristics (peak output resistance, r0 = 2000 Ω), and high mechanical flexibility (strain limits of 1%). These values of μFE and r0 are unprecedented in flexible GFETs. Flexible radio frequency FETs (RF-FETs) with channel lengths of 375 nm demonstrate μFE = 2200 cm(2) V(-1) s(-1) and r0 = 132.5 Ω. Unity-current gain frequencies, fT, and unity-power gain frequencies, fmax, reach 12.0 and 10.6 GHz, respectively. The corresponding ratio of cutoff frequencies approaches unity (fmax/fT = 0.9), a record value for flexible GFETs. Intrinsic fT and fmax are 29.7 and 15.7 GHz, respectively. The outstanding electronic characteristics are attributed to the improved dielectric environment provided by full hBN encapsulation of the graphene channel in conjunction with an optimized, self-aligned device structure. These results establish hBN as a mechanically robust dielectric that can yield enhanced electronic characteristics to a diverse array of graphene-based flexible electronics.

Highly effective removal of Cu(II) by triethylenetetramine-magnetic reduced graphene oxide composite

In the present paper a new type of triethylenetetramine-magnetite reduced graphene oxide (TET-MRGO) composite showing a high adsorption capacity (209.1mgg−1) toward Cu(II) ions was prepared. The morphological, structural, and magnetic properties of TET-MRGO were characterized using infrared spectrometer, X-ray diffraction, Scanning Electronic Microscope, nitrogen adsorption–desorption measurement, Raman spectroscopy, and Transmission Electron Microscopy. TET-MRGO exhibits strong saturation magnetization (42.13emug−1) and can be easily separated from aqueous solution by an external magnetic field. A series of batch adsorption experiments were systematically conducted to study the adsorption property of TET-MRGO. The high adsorption capacity, excellent selectivity, and effective adsorption–desorption results indicated the prepared TET-MRGO composite could be an effective adsorbent for removing Cu(II) ions from aqueous solution.

Neural adaptive control for uncertain MIMO systems with constrained input via intercepted adaptation and single learning parameter approach

This paper focuses on the problem of semi-globally stable neural adaptive control for a class of uncertain multi-input/multi-output nonlinear systems in the presence of strong interconnection, input saturation, and external disturbance. Radial basis function neural networks are utilized in the online learning of uncertain dynamics. The features of the scheme developed can be briefly summarized as follows: (1) The problem of “explosion of complexity” caused by the repeated differentiations of virtual controllers in traditional backstepping design is circumvented via the pioneering dynamic surface control technique; (2) the subsystem in the whole system can be any order, and only one scalar is needed to be online updated when dealing with uncertain dynamics and external disturbance, which is computationally inexpensive from the perspective of practical application; and (3) the bounds of transient and ultimate tracking errors are adjusted by the design parameters in an explicit form with input saturation in effect by virtue of the novel intercepted adaptation approach. It is proved via Lyapunov stability theory that all the closed-loop signals are guaranteed semi-globally uniformly ultimately bounded, and simulation results are presented to verify the effectiveness of the proposed method.

Optimalisasi Informasi Citra T1 W1 Post-Contrast Dengan Fat Saturation dan Pengaturan Time Repetition: Studi pada Pemeriksaan Magnetic Resonance Imaging Brain dengan Kasus Tumor

Background: Fat saturation is an alternative technique to improve image information in T1 WI post contrast MRI of brain tumor. It can increase lesion conspituity by suppressing normal tissue’s signal. To optimize image information by using fat saturation, selection of Fat Saturation type and Time Repetition (TR) value are important.Objectives: to analyze the differences in T1 WI post-contrast image information in MRI of brain tumor in various type of Fat Saturation and TR value.Methods: Experimental study with factorial design conducted in Telogorejo Hospital-Semarang. Nine combinations (9 groups) of three Fat Saturation types (none, weak, and strong) by three TR values (700 ms, 750 ms, and 800 ms) were given to 12 patients of MRI brain tumor. Image informations were assessed by measuring SNR (white matter, gray matter, lesions, surrounding tissue), CNR (white matter- gray matter, white matter-CSF, gray matter-CSF, lesion- surrounding tissue), lesion conspituity, artifacts, and contrast image in general.Results: The results showed that there were significant differences in SNR of white matter, gray matter, and in surrounding tissue (p 0.05); CNR of white matter-CSF, gray matter-CSF, lesion-tissue surrounding tissue (p 0.05); and lesion conspituity (p 0.05) between groups with no sat fat, weak fat sat, and strong fat sat. There were significant differences in SNR of white matter, gray matter, and surrounding tissue (p 0.05); and CNR of white matter-CSF, gray matter-CSF, and lesion- surrounding tissue (p 0.05) between group TR 700 ms, TR 750 ms, and TR 800 ms.Conclusion: Combination of strong fat saturation and TR 700 ms can produce the most optimal image information.

Direct detection of the transient superresolution effect of nonlinear saturation absorption thin films

Using a strong nonlinear saturation absorption effect is one technique for breaking through the diffraction limit. In this technique, formation of a dynamic and reversible optical pinhole channel and transient superresolution is critical. In this work, a pump–probe transient detection and observation–experimental setup is constructed to explore the formation process directly. A Ge2Sb2Te5 thin film with strong nonlinear saturation absorption is investigated. The dynamic evolution of the optical pinhole channel is detected and imaged, and the transient superresolution spot is directly captured experimentally. Results verify that the superresolution effect originates from the generation of an optical pinhole channel and that the formation of the optical pinhole channel is dynamic and reversible. A good method is provided for direct detection and observation of the transient process of the superresolution effect of nonlinear thin films.