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Duration of the Shortest Laser Pulse

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Encyclopedia of Laser Physics and Technology Pulses. May 19, 2005. "For example, a Gaussian pulse with a center frequency of 300 THz (corresponding to a wavelength of 1000 nm) can easily have a bandwidth of 30 THz, and this already corresponds to a pulse duration of about 15 fs (femtoseconds) or 0.000000000000015 seconds if the pulses are transform-limited. The shortest optical pulses generated directly in lasers have durations around 5 fs. Pulse compression techniques get down to very few femtoseconds, and high harmonic generation even allows the generation of attosecond pulses." 5 fs
Physics Web Optics enter the single-cycle regime. May 19, 2005. "Physicists at Stanford University in the US have produced the shortest ever laser pulse at optical frequencies. The pulse lasts for just 1.6 femtoseconds, which corresponds to just .8 of an optical cycle for pulses with a central wavelength of 650 nanometres." 1.6 fs
Physics Web Experimental attosecond science makes its debut. May 19, 2005. "Since the mid-1980s there have been many advances in laser science, but the minimum pulse duration has decreased only slightly. To significantly break the current record- a 4.5 femtosecond pulse from a laser with a wavelength of 800 nanometres- a completely different approach is needed." 4.5 fs

Light Amplification by Stimulated Emission of Radiation also known as LASER is a popular technology that has been used in many fields of study. Lasers which were first constructed in 1960 produce monochromatic light and use the process of stimulated emission to amplify light waves. This process causes an atom to become excited as energy is forced into the laser. Then as the atom falls back, it strikes another atom stimulating it to emit energy. This emission is in the form of a second wave that travels parallel and in step with the first wave.

When lasers were first introduced their popularity gradually emerged in different fields such as medicine, chemistry, communication, music, and much more. Lasers have become very useful and they are even in places we would not expect, such as in a typical CD player or CD-ROM. Many advantages have come from lasers and every year physicists try to improve their technology. The current challenge experts are facing is trying to change the duration of the laser pulse to a shorter femtosecond (10−15) time.

Since the mid '80s the shortest pulse was recorded to be 6 femtoseconds, but in the past decade more advanced methods have been used, including modelocking and high harmonic generation. Modelocking is a common technique in optics by which a laser can be made to produce pulses of extremely short duration. The Ti-sapphire lasers have used this technique and have directly produced pulses that were about 5 femtoseconds long. Thanks to modelocking the laser pulse in 1999 reached an all time low of 4.5 femtoseconds, and had stayed constant for several years afterwards. It was not until recently in February of 2005 when physicists at Stanford University produced even shorter pulse durations of 1.6 femtoseconds. Although 1.6 femtoseconds is already a very short duration, the more advanced technique of high harmonic generation may even be able to produce pulses as short as 100 attoseconds (0.1 femtoseconds). By creating shorter laser pulses physicists will be able to explain many types of phenomena.

The advantages that come with shorter pulse durations help physicists to study and understand the motion of atoms in molecules during physical, chemical, and biological reactions. By these studies we can understand much more about the world and we may be able to become advanced in different fields. There are still some things we will not be able to know without even shorter laser pulses, but experts are hoping that in the future there will be more laser improvements.

Larisa Tuchinskaya -- 2005