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This paper presents a detailed investigation of the physical mechanisms underlying the disruption of a lithium niobate electrooptic modulator by RF pulses. It is shown that short-term modulator disruption is a direct consequence of resistive heating within the metal conductor of the coplanar waveguide electrode, which leads to a thermo-optic optica...
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Context 1
... relates the relative phase change to the refractive index distribution at y = 0. This simplifies analysis by reducing the problem to that of finding the refractive index distribution in a 2D plane at y = 0. Dimensions used in the thermal simulations were based on microscope measurements of the modulator (with the modulator package opened after completion of the tests), and are listed in Table 1. Also listed are material properties from references [21][22][23][24][25][26], with those of the polymer buffer layer estimated from a range of typical values. ...
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... excellent agreement between simulation and experiment clearly demonstrates that the observed RF-induced transients were a thermo-optic response to resistive heating within the CPW conductors. Figure 11 plots the sensitivity of the thermally-induced phase change to the electrode- waveguide center-to-center offset, ∆z offset ≡(z 2 -z 1 )/2, determined from simulations with the properties in Table 1, and the RF pulse energy denoted as U pulse . The figure shows that the thermo-optic phase change scales linearly with ∆z offset for small offsets, which in turn implies that some reduction in short-term RF disruption may be possible through careful alignment of the RF and optical waveguides. ...
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... the properties in Table 1, and for simplicity neglecting their temperature dependence, this yields the value 2.5x10 4 K/J at the RF input, y = 0. In the previous study [7], long-term disruption occurred at the pulse energy 1 mJ, which translates to an initial temperature change of 25 K. Permanent damage was later observed at the pulse energy 8 mJ, which corresponds to an initial temperature change of 200 K. ...
Similar publications
We propose and demonstrate error-free conversion of a 40 Gbit/s optical time division multiplexed signal to 4 x 10 Gbit/s wavelength division multiplexed channels based on cascaded second harmonic and difference frequency generation in a periodically poled lithium niobate waveguide. The technique relies on the generation of spectrally (and temporal...
Citations
... LNAs diminish the considerable bandwidth advantage of using MPLs and add to the power consumption, system size, and vulnerability to electromagnetic interference effects. It is desired to improve gMPL by removing the need for LNA [19,29,30] specially in applications such as compact antenna sites [31,32], optoelectronic oscillators [18], and handling high power electromagnetic pulse effects [33]. ...
Modulators within Microwave photonic links (MPLs) encode Radio Frequency (RF) signal information to the optical domain for transmission in applications such as wireless access networks and antenna remoting exploiting advantages optical fiber offers over RF coaxial cables including bandwidth, loss, size, weight, and immunity to electromagnetic interference. A critical figure-of-merit in MPLs is spur-free-dynamic-range (SFDR) defining the range of RF signal power a MPL transmits without distortion. Current Mach-Zehnder Interference (MZI) modulators used in MPLs limit the SFDR because of the associated nonlinear sinusoidal transfer function. A rigorous theoretical method is developed followed by design, fabrication, and testing to investigate a linear ring resonator modulator (RRM) modulator for MPLs. The linear nature of the Lorentzian transfer function for the RRM is utilized over the sinusoidal transfer function within MZI modulators offering significant improvement in MPL SFDR. A novel bias voltage adjustment method is developed for practical implementations improving SFDR of 6 dB versus MZI at 500 MHz noise bandwidth. RRM is shown to be applicable for applications requiring high operational frequencies while in a limited operational bandwidth such as millimeter-wave wireless networks. To improve RRM SFDR in wide operational bandwidths a novel dual ring resonator modulator (DRRM) design is demonstrated. DRRM suppresses the third order intermodulation distortion in a frequency independent process removing SFDR limits of RRM.
... These studies have shown that the devices are radiation-resistant to X-rays up to a dose of ~10 5 rad [12], while damage due to high-energy electrons (~16 -17 MeV) is dependent on the electron irradiation rate [13,14]. Schermer et al. also reported dielectric breakdown and thermo-optic damage from high-power microwave (HPM) pulses, showing that prolonged resistive heating will result in both transient and possibly permanent damage of an electro-optic modulator [15]. The above pioneering research provides useful information and insight into the robustness of bulk materials; nevertheless, a comprehensive study of radiation damage on thinned, sliced devices and their corresponding EO responses has not yet been reported. ...
Helium-ion-induced radiation damage in a LiNbO3-thin-film (10 μm-thick) modulator is experimentally investigated. The results demonstrate a degradation of the device performance in the presence of He⁺ irradiation at doses of ≥ 10¹⁶ cm⁻². The experiments also show that the presence of the He⁺ stopping region, which determines the degree of overlap between the ion-damaged region and the guided optical mode, plays a major role in determining the degree of degradation in modulation performance. Our measurements showed that the higher overlap can lead to an additional ~5.5 dB propagation loss. The irradiation-induced change of crystal-film anisotropy ( n o − n e ) of ~36% was observed for the highest dose used in the experiments. The relevant device extinction ratio, VπL, and device insertion loss, as well the damage mechanisms of each of these parameters are also reported and discussed.
... These studies have shown that the devices are radiation-resistant to X-rays up to a dose of ~10 5 rad [12], while damage due to high-energy electrons (~16 -17 MeV) is dependent on the electron irradiation rate [13,14]. Schermer et al. also reported dielectric breakdown and thermo-optic damage from high-power microwave (HPM) pulses, showing that prolonged resistive heating will result in both transient and possibly permanent damage of an electro-optic modulator [15]. The above pioneering research provides useful information and insight into the robustness of bulk materials; nevertheless, a comprehensive study of radiation damage on thinned, sliced devices and their corresponding EO responses has not yet been reported. ...
Helium-ion-induced radiation damage in a LiNbO3-thin-film (10 mu m-thick) modulator is experimentally investigated. The results demonstrate a degradation of the device performance in the presence of He+ irradiation at doses of >= 10(16) cm(-2). The experiments also show that the presence of the He+ stopping region, which determines the degree of overlap between the ion-damaged region and the guided optical mode, plays a major role in determining the degree of degradation in modulation performance. Our measurements showed that the higher overlap can lead to an additional similar to 5.5 dB propagation loss. The irradiation-induced change of crystal-film anisotropy(n(o) - n(e)) of similar to 36% was observed for the highest dose used in the experiments. The relevant device extinction ratio, V pi L, and device insertion loss, as well the damage mechanisms of each of these parameters are also reported and discussed. (C)2014 Optical Society of America
... While many links have been demonstrated to have low NF and high spurious-free dynamic range (SFDR), it is difficult to achieve both simultaneously over multiple octaves. For numerous applications, such as high power electromagnetic pulse management 8 , integration with antennas 9,10 , high-efficiency RF power generation 11 and optoelectronic oscillators 12 , photonic solutions without front end RF amplifiers are desirable. There was a strong push in the past decade to achieve low NF fiber-optic links without electronic amplification, resulting in reported NF < 10 dB at frequencies as high as 12 GHz [13][14][15] . ...
... (Left) Required OIP2 for a photodiode such that an IMDD link at quadrature remains third-order limited given by(8) with(5) inserted for N out as a function of I dc,q with various values of B e . For these curves, φ dc = π/2,T = 290 K, R = 50 Ω, V π = 10 V and RIN laser = -300 dBc/Hz (negligible). ...
High-performance analog photonic links are discussed and the prevalent
modulation formats are highlighted. Because of its multi-octave and
millimeter-wave potential, special attention is given to intensity
modulation with direct detection (IMDD) employing an external
Mach-Zehnder modulator (MZM). The theory for IMDD is reviewed and some
experimental results are discussed. Two limiting factors in multi-octave
IMDD implementations are quantified. The MZM bias requirements in order
to remain third-order limited are shown to be very stringent in
high-performance links. Photodiode nonlinearities, perhaps the most
inhibiting factor in present-day wideband analog photonics, are cast in
terms of output intercept points and tied to the IMDD link performance.
... In this section we propose a simplified and accurate model to evaluate the performance of different phase shifter structures in a reduced time. In silicon depletion-based modulators the effective index variation Δn eff is low and can be approximated by [12]: ...
An original method to simulate depletion-based silicon modulators based on an analytical description of the active region is presented. This method is fast and efficient in particular for performance optimization. It is applied for a lateral diode integrated in a rib waveguide, and a comparison is performed with classical 2D numerical simulation. A very good agreement is obtained, showing the accuracy and efficiency of this analytical method.
Electro-optic modulators (EOMs) are an interface between electrical and optical components, making them susceptible to external electromagnetic interference (EMI). In this article, we investigate the effects of low-frequency (
${\sim }$
15 MHz) EMI on lithium niobate (LiNbO
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) EOMs. A predictive model for low-frequency EMI injection into a commercially available EOM is developed and validated experimentally. Specifically, analytical expressions for eye height and Q-factor are derived that predict the changes in the receiver end eye diagram, when the EOM modulation process is interrupted by the RF injection. The eye diagram gradually closes down as the RF injection power increases, owing to the signal degradation in the receiver end. A simple expression for calculating the maximum peak RF injected voltage that the EOM can tolerate prior to the system experiencing significant bit error rate is also presented. This model can be utilized to assess the survivability of EOMs under EMI.
BACKGROUND: The existed femoral head necrosis (FHN) model can not reflex the clinical necrosis of femoral head correctly. Microwave heating provides a new approach for model preparation, but the concrete standard remains uncertain. OBJECTIVE: To study the optimal temperature and time in preparing a FHN model induced by microwave heating. METHODS: Totally 48 rabbits were randomly divided into 4 groups on the basis of the microwave temperature (50, 55, 60°C) and heating time (10, 20 minutes). The microwave antenna was inserted into the rabbit femoral head. The rabbits were sacrificed immediately and at 1, 2, 4, 8 and 12 weeks after operation. A series of examinations were performed including gross observation, X-ray, histology and MRI to observe the femoral head necrosis and repair status. RESULTS AND CONCLUSION: Marrow partially solidified in the group (50 °C, 10 minutes) at 1 week, and the osteonecrosis returned to normal at 8 weeks after operation. In the group (55 °C, 10 minutes), marrow was completely coagulated at 1 week and low signal on T1 weighted images and increased signal on T2 images were identified at 2 weeks. Osteonecrosis and repair occurred at the same time at 4 weeks. At 12 weeks, the osteonecrosis continued and the repair stopped, and the femoral heads started to collapse. All femoral heads collapsed at 8 weeks in group (50 °C, 20 minutes) and group (60°C, 10 minutes). Accordingly, microwave heating is a good method in developing FHN model. 55 °C and 10 minutes are the optimal temperature and time for the development of FHN model of rabbits induced by microwave heating.
High-speed Mach-Zehnder interferometer silicon modulators were exposed to a total ionizing dose of 1.3 MGy, levels comparable to the worst radiation levels for a tracking detector after 10 years of operation at the High-Luminosity LHC, show a sensitivity to ionizing radiation after exposure to a dose of a few hundred kGy. A physical model to describe the effect of ionizing radiation on the modulators has been developed and is used to predict whether a more radiation-hard modulator can be designed to survive the harshest radiation environments expected at the HL-LHC.
A new optimization method is described and performed on high-speed silicon optical modulators based on carrier depletion in a p-i-n junction. Quantitative results on the geometry of the waveguide and doping concentrations of the pand n-doped regions are presented at the end of the optimization. General rules can thus be applied to design high performances optical modulators in term of modulation efficiency and insertion loss. Complete electro-optical simulations have been performed on optimal designs to evaluate the corresponding Figures of Merit and theoretical limits on performances have been exhibited. VpiLpi as low as 1.25 V.cm has been obtained at best for the p-n configuration, for a bias of 5 V and for a rib height of 400 nm. A strong dependence of the total optical loss with the geometry of the waveguide has also been demonstrated with an optimal value of 3 dB.
