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Digital frequency modulation. (a) bit sequence, (b) optical power emitted in the ^ x polarization, (c) signal recovered with a second order Butterworth lter with 1.5 GHz band-pass centered at 3.1 GHz, (d) same as (c) but centered at 1.6 GHz. Same parameters as in Fig. 1.
Source publication
The possibility of generating low chirped, fast optical pulses with linear polarization in vertical-cavity surface-emitting lasers (VCSELs) is numerically explored. We show that, under the influence of an axial magnetic field, polarization modulation at gigahertz rates can be achieved with possible applications in optical clock generation/extractio...
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... of modulating the carrier frequency of the optical eld here the rotating frequency of the polarization orientation is modulated. Although the total emitted power remains constant, the modulation of the magnetic celd leads to a modulation of the rotation frequencyy hence the repetion rate for the pulses in each polarization is modulated. In Fig. 3 we show t h e results for such a transmission scheme for a 500Mb/s pseudo-random NRZ bit stream, where the magnetic-induced circular birefringence is digitally modulated between 4.7 ns ;1 for \0" bits and 9.4 ns ;1 for \1" bits, leading to pulsation frequencies f 0 1:5 G H z for \0" bits and f 1 3 GHz for \1" bits. A portion of the bit ...
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We describe the development of a broadband magneto-optical spectrometer with femtosecond temporal resolution. The absorption spectrometer is based on a white-light supercontinuum (ca. 320 - 750 nm) using shot-to-shot temporal and spectral referencing at 1 kHz. Static and transient absorption spectra using circularly polarised light are collected in...
Citations
... More recently, Gaiffe et al. [7] have developed a magnetic circuit which allowed fields up to 1 T to be applied to a commercial 850 nm QW VCSEL, and have reported nonlinear behavior of the polarization with field strength; the effect becomes more significant with increasing laser current. Periodic pulsed output with linear polarization at a frequency of approximately Ω z ∕π (where Ω z is the circular birefringence rate caused by an axial magnetic field) has been predicted numerically by van der Lem et al. [8] in the case when the circular birefringence is greater than the intrinsic linear birefringence. ...
... where I jẼ j 2 , 2κ τ −1 p , and γ τ −1 n , with τ p and τ n as the photon and electron lifetimes, respectively; α is the linewidth enhancement factor, γ s is the spin relaxation rate, γ a is the gain anisotropy or dichroism rate, γ p is the linear birefringence rate, and ⃗ Ω is the Larmor frequency which is proportional to the magnetic field ⃗ B [6,8,11]. Here, Ω x , Ω y are the transverse magnetic field components and Ω z is the axial component. In the case of an axial magnetic field, Ω z also represents the magnetically induced circular birefringence [3][4][5] which, in the case of proton-implanted 850 nm QW VCSELs, has been found to depend linearly on the strength of the magnetic field as [6] dΩ z dB 8.3 rad ns −1 T −1 : ...
... (1)-(3) and (6) have been solved numerically using the Runge-Kutta method. The strength and direction (sign) of the axial magnetic field, Ω z (also known as the circular birefringence [3][4][5]8,11]), are taken into account in this study, while the transverse magnetic field components, Ω x and Ω y , are set to 0 [thus removing Eqs. (4) and (5)]. ...
The spin flip model is used to investigate the effects of an axial magnetic field on the polarization and dynamics of conventional vertical cavity surface-emitting lasers (VCSELs) and spin-VCSELs where polarized optical pumping is used to inject a spin-polarized electron population. It is found that the ratio of the circular birefringence caused by the magnetic field to the intrinsic linear birefringence plays an important role in exciting oscillations in the intensities and polarization of the VCSELs studied. For a conventional VCSEL, higher values of the linear birefringence require larger axial magnetic fields to cause output power and polarization oscillations. In the case of spin-VCSELs, it is found that both magnitude and sign of the magnetic field can affect the stability and dynamics, as represented on maps in the plane of polarization ellipticity versus magnitude of the pump. A reversal in the sign of the field is equivalent to reversing the sign of the pump ellipticity. Potential applications of these effects in terms of optical oscillators and magnetic field sensors are identified.
Large broadband asynchronous transfer mode (ATM) switching nodes require novel hardware solutions that could benefit from the inclusion of optical interconnect technology, since electronic solutions are limited by pin out and by the capacitance/inductance of the interconnections. We propose, analyze and demonstrate a new three stage free space optical switch that utilizes vertical cavity surface emitting lasers (VCSELs) for the optical interconnections, a liquid crystal spatial light modulator (SLM) as a reconfigurable shutter and relatively simple optics for fan out and fan in. A custom complementary metal oxide semiconductor (CMOS) chip is required to introduce a time delay in the optical bit stream and to drive the VCSELs. Analysis shows that the switch should be scalable to 1024Ã1024, which would require 2048 â¼2 mW VCSELs. {copyright} {ital 1999 Society of Photo-Optical Instrumentation Engineers.}
The characteristics of polarization self-modulation in a vertical-cavity surface-emitting laser (VCSEL) were studied for frequencies up to ≈ 9 GHz both experimentally and theoretically. Polarization self-modulation was obtained by rotating the linearly polarized output of the VCSEL by 90° and reinjecting it into the laser. Experimentally we simultaneously recorded time traces, optical and radio-frequency spectra. We found for increasing modulation frequencies that the output characteristics changed from square-wave to sinusoidal and the VCSEL system assumed new polarization eigenstates that are different from the free-running VCSEL eigenstates. We modeled polarization self-modulation as an interband process and found a good qualitative agreement between our experimental and numerical results. © 1998 American Institute of Physics.
We discuss how the polarization dependence of the saturation in
vertical-cavity surface emitting lasers (VCSELs) can be influenced by
the design of the quantum-well (QW) gain medium. As an important concept
in our discussion, we use carrier reservoirs, i.e., we separate the
carrier population into a number of subpopulations. Specifically, we
treat VCSELs in which the carriers are separated on the basis of their
spin, their momentum, or on the basis of their spatial position. By
numerically analyzing the rate equations for one specific case, we show
how a properly chosen polarization dependence of the saturation leads to
polarization self-modulation
