11:30 〜 11:45
▲ [19a-H116-11] An all-optical three terminal device based on photo-excitation of magnetization
キーワード：optical device,magneto-optical effect,photo-magnetism
Optical integrated circuit has become a matter of serious target in research and development. Magnetic materials will have their turn on optical isolators, as exemplified in the Mach-Zehnder interferometer (MZI) incorporating the non-reciprocal phase delay due to magneto-optical (MO)
effect . Here, we consider the reconstruction of the MO-MZI device from passive to active by introducing photo-induced magnetism. Let us assume that a magnetization vector M on one side of MZI is pointing parallel to the optical axis of the waveguide (WG), as shown schematically in Fig. 1. Here, the difference in the optical length between two different WGs is controlled in such a way to yield the destructive interference condition. Optical excitation of M with fs-laser pulses dynamically alters the direction of M, causing temporal variation of the interference condition and thus gating the pulse train R entering from the port X to yield output pulses R* from the opposite port Z. An all-optical three terminal device can be realized, if the pulse quality (energy and shape) of R* is not degraded severely compared with the input (excitation) pulses S.
One of the candidate phenomena which enable us to manipulate M with relatively low excitation energy is photo-excited precession of magnetization (PEPM). Cone angles of the PEPM range 0.02-0.2 rad. with excitation of 10 mJ/cm2 per 150 fs-pulse (l = 790 nm) in Co/Pd ultrathin multi-layers (uML).
Feasibility of the proposed device has been examined by numerically calculating mode-propagation in the GaAs-based MZI with optical path difference (delta)L [mm] and the MO-induced phase shift
(delta)(phai) = Db LM×sin(theta). Here, Db = -0.25 [rad/mm], LM the length of a Co/Pd uML slab, and (theta) the in-plane angle with respect to the optical axis of WG. It is clearly seen that optical transmission can be varied with (theta). In view of binary threshold detection, proper adjustment of initial (theta) is needed to code/decode a small cone angle induced by PEPM. Calculation for the transmission of a Gaussian pulse (FWHM of 120 fs) suggests a relative change in transition of around ±2 dB when (theta) = 0.2 rad. and (delta)(theta) = ±0.1 rad. are assumed.
effect . Here, we consider the reconstruction of the MO-MZI device from passive to active by introducing photo-induced magnetism. Let us assume that a magnetization vector M on one side of MZI is pointing parallel to the optical axis of the waveguide (WG), as shown schematically in Fig. 1. Here, the difference in the optical length between two different WGs is controlled in such a way to yield the destructive interference condition. Optical excitation of M with fs-laser pulses dynamically alters the direction of M, causing temporal variation of the interference condition and thus gating the pulse train R entering from the port X to yield output pulses R* from the opposite port Z. An all-optical three terminal device can be realized, if the pulse quality (energy and shape) of R* is not degraded severely compared with the input (excitation) pulses S.
One of the candidate phenomena which enable us to manipulate M with relatively low excitation energy is photo-excited precession of magnetization (PEPM). Cone angles of the PEPM range 0.02-0.2 rad. with excitation of 10 mJ/cm2 per 150 fs-pulse (l = 790 nm) in Co/Pd ultrathin multi-layers (uML).
Feasibility of the proposed device has been examined by numerically calculating mode-propagation in the GaAs-based MZI with optical path difference (delta)L [mm] and the MO-induced phase shift
(delta)(phai) = Db LM×sin(theta). Here, Db = -0.25 [rad/mm], LM the length of a Co/Pd uML slab, and (theta) the in-plane angle with respect to the optical axis of WG. It is clearly seen that optical transmission can be varied with (theta). In view of binary threshold detection, proper adjustment of initial (theta) is needed to code/decode a small cone angle induced by PEPM. Calculation for the transmission of a Gaussian pulse (FWHM of 120 fs) suggests a relative change in transition of around ±2 dB when (theta) = 0.2 rad. and (delta)(theta) = ±0.1 rad. are assumed.