7.2 What is so Special About Femtosecond Laser?
165
• Dissipation and transfer of energy take place on a time scale greater than 100
femtosecond.
• Can provide very high peak power. Laser with 10 mJ pulse and having hundred
femtosecond duration can produce peak power 100 GW (relation: I ~ J/τ,where
I denotes the produced peak power, J and τ represent the pulse energy and pulse
duration, respectively.)
• Femtosecond laser pulse can create an ultraintense magnetic field strength of the
order of hundreds of Tesla.
7.3 Issues to Be Considered: Why Do We Need Optical
Manipulation?
To get preferred result in spintronics, many issues are to be considered and major
challenges are to be faced and overcome. Some of them are electron’s spin lifetime optimization, spin coherence detection in nanoscale structures, spin-polarized
carriers transport, etc. Challenges also include skilful management of electron and
nuclear spin in ultrafast time scale. Efficient controlling of magnetic states is the
key towards the development of high speed information storage device in magnetic
media. Magnetization manipulation requires alternative ways other than magnetic
field that will be effective at or above room temperature.
The development of femtosecond lasers, as external stimuli, has triggered the path
of ultrafast manipulation of the magnetic order (Beaurepaire et al. 1996; Kirilyuk
et al. 2010; Satoh et al. 2010, 2009, 2016; Chen et al. 2019; Wolf et al. 2001;
Pershan 1963). Thanks to Bigot and coworkers for their milestone work on ultrafast
switching in Nickel at Strasbourg in the year of 1996. Femtosecond light pulses
offer the challenging but interesting possibility of probing a magnetic system on a
time scale much faster than the time scale of spin–orbit interaction (SOI) or magnetic
precession (see Fig. 7.3). Generally the time scale for SOI is around 1–10 ps whereas
for magnetic precession, it is 100 ps–1000 ps. Ultrashort light pulse-based magnetic
Fig. 7.3 Time scales in magnetism (adapted and redrawn from Ref. (Kirilyuk et al. 2010))
165
• Dissipation and transfer of energy take place on a time scale greater than 100
femtosecond.
• Can provide very high peak power. Laser with 10 mJ pulse and having hundred
femtosecond duration can produce peak power 100 GW (relation: I ~ J/τ,where
I denotes the produced peak power, J and τ represent the pulse energy and pulse
duration, respectively.)
• Femtosecond laser pulse can create an ultraintense magnetic field strength of the
order of hundreds of Tesla.
7.3 Issues to Be Considered: Why Do We Need Optical
Manipulation?
To get preferred result in spintronics, many issues are to be considered and major
challenges are to be faced and overcome. Some of them are electron’s spin lifetime optimization, spin coherence detection in nanoscale structures, spin-polarized
carriers transport, etc. Challenges also include skilful management of electron and
nuclear spin in ultrafast time scale. Efficient controlling of magnetic states is the
key towards the development of high speed information storage device in magnetic
media. Magnetization manipulation requires alternative ways other than magnetic
field that will be effective at or above room temperature.
The development of femtosecond lasers, as external stimuli, has triggered the path
of ultrafast manipulation of the magnetic order (Beaurepaire et al. 1996; Kirilyuk
et al. 2010; Satoh et al. 2010, 2009, 2016; Chen et al. 2019; Wolf et al. 2001;
Pershan 1963). Thanks to Bigot and coworkers for their milestone work on ultrafast
switching in Nickel at Strasbourg in the year of 1996. Femtosecond light pulses
offer the challenging but interesting possibility of probing a magnetic system on a
time scale much faster than the time scale of spin–orbit interaction (SOI) or magnetic
precession (see Fig. 7.3). Generally the time scale for SOI is around 1–10 ps whereas
for magnetic precession, it is 100 ps–1000 ps. Ultrashort light pulse-based magnetic
Fig. 7.3 Time scales in magnetism (adapted and redrawn from Ref. (Kirilyuk et al. 2010))