Acoustic-optic Tunable Filter Research Articles

High-power multi-wavelength Yb-doped fiber laser with a tunable interval, amplitude, and a number of channels

In recent years, multi-wavelength lasers have attracted much attention due to their wide applications in various fields. In this Letter, we experimentally demonstrate a high-power multi-wavelength Yb-doped fiber laser with the aid of an acoustic-optic tunable filter, in which the wavelength interval, the intensity of each channel, and the number of lasing channels can be tuned independently. As a result, the operating wavelength tuning range covers 1040.0 to 1090.0 nm and the maximal output power reaches 15.7 W, which is higher than the previous reports by more than three orders of magnitude. The wavelength interval can be adjusted from 2.6 to 50 nm and the spectral profile can be arbitrarily controlled. Furthermore, the number of wavelength channels can be adjusted from 1 to 4. This work will provide a reference for achieving high-power spectral-flexible fiber sources.

Cosine apodization of dual-resonance all-fiber acousto-optic tunable filters.

We experimentally demonstrate a novel cosine apodization technique for dual-resonance all-fiber acoustic-optic tunable filter. The technique is based on a hybrid control of input acoustic polarization state and circumferential fiber twist. We will show that intrinsic sidelobe spectra occurring between dual filtering bands are successfully suppressed through our approach, which will be also theoretically confirmed via our analytical and numerical studies. The results illustrate that the spectral positions of each resonance are tuned linearly and continuously by the fiber twist, and that overall sidelobe spectra between two resonances are suppressed regardless of fiber twist angle. The proposed scheme is useful to minimize cross talk between adjacent wavelength channels in optical sensor systems. We highlight that our approach is directly applicable to low-noise matched filtering.

Note: Comparison between a prism-based and an acousto-optic tunable filter-based spectrometer for diffusive media

This paper compares two continuously tunable systems for time-resolved spectroscopy of diffusive media based on a supercontinuum laser source. Two approaches for spectral selection are considered relying either on a dispersive prism or on a commercial acoustic-optic tunable filter (AOTF) device. The comparison was performed first in terms of extracted power and spectral response function, then in terms of distortions introduced in the retrieved absorption and scattering spectra. Simulations and experiments on diffusive phantoms confirmed that, besides narrower FWHM in the AOTF bandpass, the prism solution is superior with respect to the distortions produced on the recovered spectra.

Optical Bistability in an Acousto-Optic Tunable Filter (AOTF) Operating with Short Optical Pulses

In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has shown the dependence of the hysteresis curve with the product of the coupling constant (κ) by the length of the device (ξL) and the conversion power-coupling constant factor (G). The range of bistability varies significantly with both G and with κξL parameters. The variation of κξL directly increases the size of the range of bistability hysteresis while the increase in G causes the bistability to occur at low powers. The phenomenon of optical bistability (OB) is the object of increasing interest due to its possibilities for important device applications. A bistable device is a device with a capability to generate two different outputs for a given input and the physical requirements for this are an intensity-dependence refractive index and an optical feedback mechanism.

Optical cryptography under PPM-PAM modulation based in short optical pulses in an acoustic-optic tunable filter (AOTF)

A new optical encryption method using an acousto-optic tunable filter (AOTF) operating simultaneously with pulse position modulation (PPM) and pulse amplitude modulation (PAM) is proposed in this paper. This device operates with ultrashort soliton light pulses (2ps), which are modulated in agreement with the technique of pulse modulation just mentioned. In this way any pulse carries naturally two bits of information but when the encryption proposed here, is applied, each encrypted pulse, carries four bits of information. We have analyzed the sixteen output possible situations, modulating the input pulses polarized in TE and TM modes allowing a variation in the PPM \({(\varepsilon_{\rm PPM})}\) and PAM \({(\varepsilon_{\rm PAM})}\) parameters for each modulation. We have defined all the possibility pairs of PPM-PAM parameters where the encrypting procedure is possible.

Quantifying RhoA Facilitated Trafficking of the Epithelial Na+ Channel toward the Plasma Membrane with Total Internal Reflection Fluorescence-Fluorescence Recovery after Photobleaching

The epithelial Na(+) channel (ENaC) plays a central role in control of epithelial surface hydration and vascular volume. Similar to other ion channels, ENaC activity is set, in part, by its membrane levels. The small G protein RhoA increases ENaC activity by increasing the membrane levels of this channel. We hypothesize that RhoA increases ENaC activity by promoting channel trafficking to the plasma membrane. Few experimental methods are available to directly visualize trafficking of ion channels to the plasma membrane. Here we combine electrophysiology with two complementary imaging methods, total internal reflection fluorescence microscopy and fluorescence recovery after photobleaching, to study the mechanistic basis of RhoA actions on ENaC. Patch clamp results demonstrate that RhoA increases ENaC activity in an additive manner with dominant-negative dynamin. This is consistent with a mechanism of increased ENaC trafficking to the membrane. Direct visualization of ENaC movement near the plasma membrane with total internal reflection fluorescence-fluorescence recovery after photobleaching revealed that RhoA accelerates ENaC trafficking toward the membrane. RhoA-facilitated movement of the channel was sensitive to disrupting the endomembrane system. Moreover, facilitating retrieval decreased ENaC activity but not trafficking toward the membrane. ENaC at the plasma membrane clustered and was laterally immobile suggesting that the cytoskeleton tethers or corrals membrane resident channels or membrane-directed vesicles containing ENaC. Disrupting microtubules but not microfilaments led to reorganization of ENaC clusters and slowed trafficking toward the membrane. The cytoskeleton is an established target for RhoA signaling. We conclude that RhoA, likely through effects on the cytoskeleton, promotes ENaC trafficking to the plasma membrane to increase channel membrane levels and activity.

Fluorescence of the “fire-chaser” beetle Melanophila acuminata

Melanophila acuminata beetles are attracted to forest fires over long distances by a pair of specialized infrared sensory organs. To date, there is no knowledge of their ability to detect or emit fluorescent radiation. We studied the Melanophila acuminata infrared sensory organs histologically and by using fluorescent microscopy, acoustic–optic tunable filter microscopy, and two-photon microscopy to identify fluorescence. We found fluorescent absorption at radiation wavelengths of 480 nm and emission at 570 nm. The functional role of this novel fluorescence is, as of yet, unknown but may be applied to species classification, identification and behavioral studies.

Numerical Analysis of the Crosstalk on an Integrated Acousto-Optic Tunable Filter (AOTF) for Network Applications

In this article, we did a study of the crosstalk level (Xtalk) and extinction ratio (Xratio) of an acousto-optic tunable filter (AOTF) operating with ultra-short light pulses (2 ps). It is clear that the transmission bandwidth decreases as the length of the device increases. The compression factor was studied for the switched pulse in an AOTF without loss considering five nonlinearity profiles. One can observe that there is always an optimum value for β (final value of the nonlinearity) that one can obtain a switched pulse with the same time duration of the input pulse. The study of the crosstalk level, of this device, considering the optimum values of β obtained from the compression studies, as a function of the pump power (P0) was done. For the soliton profile at 1 W of pump power one can notice that the Gaussian profile presents the lower Xtalk value (−13 dB), and the constant profile presents the worst value (−9.8 dB). However, if one is looking for a specific Xtalk value, one can conclude that with the constant profile one can obtain this value with a lower power. For the quasi-soliton profile of the same device, with low pump power (1 W), one can notice again that the Gaussian profile presents the lower Xtalk value (−13 dB) and the constant profile presents the worst value (−9.87 dB). This fact can be explained because, with pump power at 1 W, soliton and quasi-soliton profiles lead equivalent input pulses and under the same conditions produce equal results. The Xtalk level, considering all the profiles as a function of the β value, was studied. For all the profiles one has a strong increase of the Xtalk level with the increase of the final β value of the nonlinearity profile. Comparing all the profiles one can conclude that the Gaussian profile presents the lower Xtalk value in the range of β values in use. At the same time the value of the Xtalk for this profile does not change much with the change in the β value, presenting values in interval (−13 dB; −11.7 dB). The studies of the Xratio of the same device operating with the input pulses with the soliton and quasi-soliton profiles reveal that for all the nonlinearity profiles the Xratio increases with an increase in pump power. For the quasi-soliton profile one can notice that there is a minimum of the Xratio as a function of the pump power. The Xratio considering all the profiles as a function of the β value shows that for all the profiles one has a strong increase of the Xratio level with the increase of the final β value of the nonlinearity profile. Comparing all the profiles one can conclude that the Gaussian profile presents the lower Xratio value in the range of β values in use. One can conclude that the operation of the AOTF in a switching configuration is worse for high pump power as observed for Xtalk. The study of the crosstalk level and the extinction ratio on the AOTF operating with ultra-short optical solitons provides possibilities for achieving high efficiency in ultra fast all-optical signal processing, especially for optical switches, filters, and optical transistors. The acoustic-optic tunable filter (AOTF) has attracted great attention in recent years, in part because it appears to be a suitable basis for multi-wavelength optical cross-connects. It is probably the only known tunable filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multi-wavelength router.

Interchannel crosstalk on the acousto‐optic tunable filter (AOTF) for network applications

AbstractIn this paper, we present a study of the crosstalk level of an acousto‐optic tunable filter (AOTF) operating with ultrashort light pulses (2 ps). Initially, we consider the performance of the device, with several lengths, operating in the linear and nonlinear regime without loss. Given low pump power (P0 = 1 W), the crosstalk level (XL) of this device always increases with the length of the AOTF, for three different device configurations: the soliton regime, the dispersionless regime, and the linear regime. For shorter devices (L/10 < ξL < L), the soliton regime presents the lower XL. However, this behavior is reversed for longer devices, where the filter bandwidth is much shorter than the pulse bandwidth. For the dispersionless regime and low pump power, the device with length of ξL = L/10 presents the lowest XL. As one starts increasing the pump power, the XL is increases as a consequence of the increase of the switched pulse's bandwidth. One would expect that the presence of nonlinearity leads to the broadening of the pulse bandwidth associated with the self‐phase modulation and, consequently, with the increase of the XL. For high power (P0 = 9 W), the switched pulse is also presenting pulse break up. However, in the limit of high pump powers, all the devices present almost the same XL of around −1.5 dB. For the soliton regime, in all the devices there is a decrease of the XL for pump powers around 1 W, which is the energy of the fundamental soliton. For high pump powers, all devices present a second peak, where again a decrease of the XL is detected. For the ξL = L/10 device, the minimum is around 8 W. The increase of the pump power results in high‐order solitons and pulse compression; in this situation, the bandwidth of the pulse increases and we can extrapolate the bandwidth of the device, the XL as increases. The study of the effect of the XL on the AOTF, operating with ultra‐short optical solitons, provides possibilities for achieving high efficiency in ultrafast all‐optical signal processing, especially for optical switches, filters, and optical transistors. The acoustic‐optic tunable filter (AOTF) has attracted great attention in recent years, in part because it appears to be a suitable basis for multiwavelength optical cross‐connects. It is probably the only known tunable filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multiwavelength router. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 230–235, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10565

PICOSECOND PULSE SWITCHING IN AN ACOUSTO-OPTIC TUNABLE FILTER (AOTF) WITH LOSS

In this paper, we did a study of the transmission characteristics of the AOTF operating with ultrashort light pulses <$>(2\,\hbox{ps})<$>. Initially one considers the performance of the device, with several lengths, operating in the nonlinear regime without loss. It was observed that the effect of dispersion and non-linearity has strong influence on the pulse propagation when one increases the length of the AOTF. For shorter length of the device the switched pulse is presenting time broadening for soliton and non-soliton profiles. For higher length of the device, pulse breakup was observed for the non-soliton profile and time displacement for the soliton profile. Considering the device of length <$>0.25\,\hbox{mm}<$> with <$>4\,\hbox{dB/mm}<$> of loss and constructed with an increasing non-linearity profile, one can say that one can operate the AOTF in a configuration that one can avoid the pulse break up and have a switched pulse with a shorter time duration compared with the lossy AOTF. The study of the AOTF operating with ultra short optical pulses provides possibilities for achieving, high efficiency in ultrafast all-optical signal processing, especially for optical switches, filters and optical transistors. The acoustic-optic tunable filter (AOTF) has attracted great attention in recent years, in part because it appears to be a suitable basis for multi-wavelength optical cross-connects. It is probably the only known tunable filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multi-wavelength router.

Analysis of Ultrashort Pulse Switching in an Acousto-optic Tunable Filter (AOTF) with Loss

In this paper, we did a study of the transmission characteristics of the AOTF operating with ultrashort light pulses (2ps). Initially one consider the performance of the device, with several lengths, operating in the nonlinear regime without loss. It was observed that the effect of dispersion and nonlinearity has strong influence on the pulse propagation when one increase the length of the AOTF. For shorter length of the device the switched pulse is presenting time broadening. For higher length of the device, pulse breakup was observed. Considering the AOTF with 4 dB/mm of loss, one consider the device of length 0.25 mm constructed with an increasing nonlinearity profile. It was observed that the increase in β (increase of the final value of the profile Q(ξ) of the nonlinearity) lead the switched pulse from broadening to optical compression. One can say that one can operate the AOTF in a configuration that one can avoid the pulse break up and have a switched pulse with a shorter time duration compared with the lossy AOTF. The second AOTF present a higher length (0.76 mm) with higher loss (40 dB/mm) is leading the switched pulse to a strong broadening. In the presence of the nonlinear profile configuration we start having pulse break up. With the increase of the β parameter the pulse is showing break-up where the more intense pulse is shorter than the input pulse. One can say that is possible to operate the AOTF in a situation where the switched pulse present a less intense satellite pulse. The study of the AOTF operating with ultra short optical solitons provides possibilities for achieving, high efficiency in ultrafast all-optical signal processing, especially for optical switches, filters and optical transistors. The acoustic-optic tunable filter (AOTF) has attracted great attention in recent years, in part because it appears to be a suitable basis for multi-wavelength optical cross-connects. It is probably the only known tunable filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multi-wavelength router.