April 4, 2007
Furukawa Electric has been focusing on research and development of fiber-optic femtosecond pulsed light sources [Note 1], taking advantage of the cutting-edge technologies the company has accumulated in the field of optical communications. In particular, the company has received the Grant for Practical Application of Industrial Technology from the New Energy and Industrial Technology Development Organization (NEDO) for two years starting from January 2005, and succeeded in developing practical application technology for a femtosecond pulsed light source that is integrated with an unconventional function of pulse repetition frequency tuning. We intend to promote marketing this product as a next-generation light source for advanced fields such as measurement, precision machining, terahertz research [Note 2] and biomedicine while exploiting the high peak power and broadband characteristics of the optical pulses the light source can output.
Developmental Background
Picosecond and femtosecond ultra-short optical pulses are used in a variety of fundamental research fields including nondestructive, noninvasive measurement for substance properties based on nonlinear optical responses; terahertz waves generation which is recently drawing attention as a drug identification technique and as a substitute for X ray inspection; as well as ultra-precision, thermal damage-free machining of glass, metal and semiconductor with the nanometer and micrometer-scale precision; biomedical applications such as cleavage and manipulation of cells; and a light source for OCT [Note 3] and multi-photon microscopy. These technologies are expected to have practical applications in the fields of industry and medical science.
Conventionally solid lasers such as titanium-sapphire laser [Note 4] were generally used, but since these lasers are rather weak against vibration and dust, they needed clean environments with stabilized ambient temperatures. To solve these practical problems, we have applied the cutting-edge technologies we have accumulated in the field of optical communications, thereby succeeding in developing the technology for practical application of a fiber-optic femtosecond pulsed light source in the 1.55-µm band that offers high reliability as well as excellent performance in terms of user-friendliness, stability and environmental resistance.
Configuration of Femtosecond Pulsed Light Source and Technological Successes
Photo of femtosecond pulsed light source
The femtosecond pulsed light source we have developed here generates picosecond optical pulses by directly modulation driving a semiconductor laser for optical communication use by means of electrical signals, and subsequently compresses the output pulses into several hundreds femtoseconds to one hundred femtoseconds in frequency utilizing fiber-optic optical pulse compression technology that we have proprietarily developed. In this way, a femtosecond pulsed light source of simple configuration has been realized, eliminating the need for a mode-locking mechanism [Note 5] that tends to be rather unstable against environmental variations.
Moreover, the direct modulation enables arbitrary settings of repetition frequency as well as accurate synchronization with the external electric signals. Furthermore, the width of output optical pulses can be set arbitrarily by tuning the optical pulse compressor. Since all the components constituting the light source are selected from those with proven performance in the optical communications fields, and, in particular, the active components are electrically controlled, the light source developed here offers high reliability, high stability and ease of operation that was not realizable with conventional solid lasers or mode-locking lasers.
The light source including its power supply and control circuits is accommodated in a compact casing with the size of a desktop personal computer, and can be used anywhere as long as a 100-V AC power supply is available. The output port uses an optical fiber to improve ease of handling while ensuring output performance. A computer-controlled, user-friendly operational interface is provided with based on a USB connection, thereby achieving significantly practical technology.
General Characteristics
| Item | Unit | Value |
|---|---|---|
| Repetition frequency | MHz | 10~250 |
| Pulse energy | nJ | 0.5 |
| Averaged power | mW | 125 at 250MHz |
| Pulse width | Fs | < 300 |
| Unit size | mm | 325 x 291 x 127 |
| Power consumption | W | 250 |
Future Development
Based on the technology developed here, we intend to improve the output wavelength range and output power of the product, thereby building up a broad lineup of light sources for machining and analysis that incorporates the fiber-optic laser light source we have recently begun production and marketing, in order to expand the business of fiber-optic ultra-short pulsed light sources that are suited to any applications.
Glossary
Based on the technology developed here, we intend to improve the output wavelength range and output power of the product, thereby building up a broad lineup of light sources for machining and analysis that incorporates the fiber-optic laser light source we have recently begun production and marketing, in order to expand the business of fiber-optic ultra-short pulsed light sources that are suited to any applications.
- (Note 1) Femtosecond, picosecond
- One femtosecond and one picosecond are one quadrillionth and one trillionth of one second, respectively.
- (Note 2) Terahertz wave
- Electromagnetic waves with a wavelength between 30µm and 3mm, corresponding to an intermediate region between lightwave and radiowave.
- (Note 3) OCT (Optical Coherence Tomography)
- An optical tomographic imaging technique that utilizes optical coherence.
- (Note 4) Mode-locked titanium-sapphire laser
- A solid laser using a titanium-sapphire crystal that can generate, based on mode-locked oscillation, ultra-short pulses of from 10 femtoseconds to several picoseconds.
- (Note 5) Mode-locking mechanism
- One of the methods to generate femtosecond and picosecond pulses, utilizing a mechanism of phase-matched oscillation.