European Patent:Terahertz system

European Patent EP2509173
Inventor:
Sartorius, Bernd (Württembergallee, 22, 14052, Berlin, DE)

http://www.freepatentsonline.com/EP2509173B1.html

CLAIMS:

1. Terahertz system, comprising a beat signal generating device (1) which has - a first monomode laser (2) for generating radiation of a first wavelength (λ₁); - a second monomode laser (3) for generating radiation of a second wavelength (λ₂) different from the first wavelength (λ₁); - a first and a second output port (11, 12); - a phase modulating unit (4) for modifying both the phase of radiation generated by the first laser and the phase of radiation generated the second laser (2, 3), wherein the beat signal generating device (1) is configured in such a way that - the radiation generated by the first laser (2) is transmitted through the second laser (3) and superposed with the radiation generated by the second laser (2) at the second output port (12), and - the radiation generated by the second laser (3) is transmitted through the first laser (2) and superposed with the radiation generated by the first laser (2) at the first output port (11), such that - a first beat signal (A) will be emitted at the first output port (11) and a second beat signal (B) will be emitted at the second output port (12), , wherein the first output port (11) of the beat signal generating device (1) is connected to a first component of the Terahertz system, wherein the first component is a Terahertz transmitter such that the first beat signal (A) is supplied to the Terahertz transmitter, characterized in that
the second output port (12) of the beat signal generating device (1) is connected to a second component of the Terahertz system, wherein the second component is a Terahertz receiver such that the second beat signal (B) is supplied to the Terahertz receiver, wherein the phase between the first beat signal (A) supplied to the Terahertz transmitter and the second beat signal (B) supplied to the Terahertz receiver can be adjusted by means of the phase modulating unit (4). 

2. The Terahertz system as claimed in claim 1, further comprising a plurality of straight optical waveguides (111-114) connecting the first laser (2) to the first output port (11) and to the phase modulating unit (4), respectively, and connecting the second laser (3) to the second output port (12) and to the phase modulating unit (4), respectively. 

3. The Terahertz system as claimed in claim 1 or 2, wherein the phase modulating unit (4) is an electro-optical phase modulating unit arranged between the first and the second laser (2, 3). 

4. The Terahertz system as claimed in one of the preceding claims, wherein the first laser (2) is a first DFB laser and the second laser (3) is a second DFB laser, the Bragg gratings of the first and the second DFB laser being configured in such a way that the wavelength of the radiation generated by the first DFB laser lies outside the stopband of the second DFB laser and the wavelength of the radiation generated by the second DFB laser lies outside the stopband of the first DFB laser. 

5. The Terahertz system as claimed in claim 4, wherein the first DFB laser is configured to generate radiation on the long wavelength side of its stop band and the second DFB laser is configured to generate radiation on the short wavelength side of its stop band. 

6. The Terahertz system as claimed in claim 4 or 5, wherein the first DFB laser comprises a gain coupled Bragg grating. 

7. The Terahertz system as claimed in one of the claims 4 to 6, wherein the second DFB laser comprises an index coupled Bragg grating. 

8. The Terahertz system as claimed in one of the claims 4 to 7, wherein - the first DFB laser comprises at least a first and a second section having a first and a second Bragg grating, wherein the Bragg wavelengths and the widths of the stop bands of the first and the second Bragg grating differ in such a way that only the wavelengths of the long wavelength modes in the first and the second section compare, and/or - the second DFB laser comprises at least a first and a second section having a first and a second Bragg grating, wherein the Bragg wavelengths and the widths of the stop bands of the first and the second Bragg grating differ in such a way that only the wavelengths of the short wavelength modes in the first and the second section compare. 

9. The Terahertz system as claimed in one of the preceding claims, wherein the first and/or the second laser (2, 3) comprises means for tuning the wavelength of the generated radiation. 

10. The Terahertz system as claimed in claims 8 and 9, wherein the means for tuning the wavelength are configured in such a way that - the Bragg wavelength of at least one of the first and the second Bragg grating of the first DFB laser can be altered such that the overlap of the long wavelength modes can be switched to an overlap of the short wavelength modes, and/or - the Bragg wavelength of at least one of the first and the second Bragg grating of the second laser can be altered such that the overlap of the short wavelength modes can be switched to an overlap of the long wavelength modes. 

11. The Terahertz system as claimed in claim 9 and 10, wherein the means for tuning the wavelength comprise - a first heating element assigned to the first section of the first DFB laser and a second heating element assigned to the second section of the first DFB laser such that the Bragg wavelength of the first and the second Bragg grating of the first DFB laser can be altered independently from one another; and/or - a first heating element assigned to the first section of the second DFB laser and a second heating element assigned to the second section of the second DFB laser such that the Bragg wavelength of the first and the second Bragg grating of the second DFB laser can be altered independently from one another. 

12. The Terahertz system as claimed in one of the preceding claims, further comprising a mode transforming device (51, 52) for transforming the spatial intensity distribution of the radiation generated by the first and/or the second laser (2, 3) into a modified spatial intensity distribution. 

13. The Terahertz system as claimed in one of the preceding claims, further comprising an amplifying device (71, 72) for amplifying the radiation generated by the first and/or the second laser (2, 3). 

14. Use of a beat signal generating device (1), wherein the beat signal generating device (1) comprises - a first laser (2) for generating radiation of a first wavelength (λ₁); - a second laser (3) for generating radiation of a second wavelength (λ₂) different from the first wavelength (λ₁); - a first and a second output port (11, 12); - a phase modulating unit (4) for modifying both the phase of radiation generated by the first laser (2) and the phase of radiation generated the second laser (3), wherein the beat signal generating device (1) is configured in such a way that - the radiation generated by the first laser (2) is transmitted through the second laser (3) and superposed with the radiation generated by the second laser (3) at the second output port (12), and - the radiation generated by the second laser (3) is transmitted through the first laser (2) and superposed with the radiation generated by the first laser (2) at the first output port (11), such that a first beat signal (A) will be emitted at the first output port (11) and a second beat signal (B) will be emitted at the second output (12) port, characterized in that
the beat signal generating device (1) is used to control a Terahertz system, wherein the first output port (11) of the beat signal generating device (1) is connected to a first component of the Terahertz system and the second output port (12) of the beat signal generating device (1) is connected to a second component of the Terahertz system, the first component being a Terahertz transmitter and the second component being a Terahertz receiver, wherein the first beat signal (A) is supplied to the Terahertz transmitter and the second beat signal (B) is supplied to the Terahertz receiver, and wherein the phase between the first and the second beat (A, B) signal is adjusted by means of the phase modulating unit (4). 

Fraunhofer unveils new time-domain THz system for commercial use

Touchless and Non-destructive – Fiber optic terahertz screens materials and analyses substances

http://www.hhi.fraunhofer.de/en/project-of-the-month/fiber-optic-terahertz-screens-materials-and-analyses-substances/

Fraunhofer HHI has developed a complete system for the mobile, flexible and low-cost practical use of terahertz radiation in industrial environments. This complete system is based on a chip developed by Fraunhofer HHI in combination with components and technologies originally developed for fiber optic telecommunications.

THz combines the characteristics of radio waves and infrared light

Terahertz, or THz for short, is a frequency band which until only recently was very difficult to exploit. In the electromagnetic spectrum THz is precisely situated between radio waves and infrared light and combines the characteristics of these two frequencies. This particular combination means that the radiation – which is completely safe for humans – can penetrate and analyze materials and substances, thus opening up a new range of possibilities.

Mobile and affordable – terahertz as a complete system

Terahertz sensor systems are at a premium when it comes to non-destructive investigation of the insides of materials. Only terahertz systems used to be heavy, cumbersome and complex, and a great deal of serious development went into terahertz technologies before the apparent good qualities of terahertz could be harnessed for practical uses in industrial environments at acceptable costs. With its "TeraWave Time Domain Spectrometer" complete system Fraunhofer HHI has now found a way with a system that integrates all the components and processes required for its mobile, flexible real-world usage.

                        Developed by Fraunhofer HHI, the "TeraWave Time Domain Spectrometer" complete system packs all    the components and processes needed (Photo: Fraunhofer HHI)

A new chip from Fraunhofer HHI tones up THz for real-world usage

The control unit of the complete systems contains telecom-developed lasers which emit ultra-short light pulses on what is known as the "Telecom wavelength" of 1.5 µm. This laser light is sent via flexible standard fiber optic cable to moveable THz emitter and detector heads. What is really crucial here are the Opto-Chips built into these THz heads.

Fraunhofer HHI THz sensor systems can be flexibly integrated into fabrication workflows

For realization of the complete system, Dr. Bernd Sartorius, group manager of Terahertz Technology at Fraunhofer HHI, and his team have integrated these chips in fiber-coupled flexible emitter and detector modules. As Bernd Sartorius explains, "Our system takes terahertz out of the lab environment. Our terahertz sensors can be flexibly integrated in a huge variety of fabrication and monitoring workflows. Control and evaluation is done by the laptop."

Terahertz at work

Monitoring the production and processing of plastics is one important area of use for terahertz sensors. In the food industry mobile complete systems can be used to scan packaging and foodstuffs to monitor the quality of contents. Unlike metal detectors, this system can even detect non-metallic materials like splinters of glass in chocolate.

The new technology is also ideal for the scanning of letters and packets to detect possible bio-weapons or explosives. The photo below shows a powder-filled plastic pouch between two sections of corrugated cardboard representing part of a packet. The THz emitter and detector heads developed by Fraunhofer HHI conduct a THz spectroscopic analysis of the powder. The THz transmission spectrum on the left shows an absorption band which identifies the powder as harmless lactose.

       THz irradiates packages like corrugated cardboard boxes and can make a spectroscopic analysis of the materials inside. (Photo: Fraunhofer HHI)

Fraunhofer HHI has developed a complete system for the mobile, flexible and low-cost practical use of terahertz radiation in industrial environments. This complete system is based on a chip developed by Fraunhofer HHI in combination with components and technologies originally developed for fiber optic telecommunications.

THz combines the characteristics of radio waves and infrared light

Terahertz, or THz for short, is a frequency band which until only recently was very difficult to exploit. In the electromagnetic spectrum THz is precisely situated between radio waves and infrared light and combines the characteristics of these two frequencies. This particular combination means that the radiation – which is completely safe for humans – can penetrate and analyze materials and substances, thus opening up a new range of possibilities.

Mobile and affordable – terahertz as a complete system

Terahertz sensor systems are at a premium when it comes to non-destructive investigation of the insides of materials. Only terahertz systems used to be heavy, cumbersome and complex, and a great deal of serious development went into terahertz technologies before the apparent good qualities of terahertz could be harnessed for practical uses in industrial environments at acceptable costs. With its "TeraWave Time Domain Spectrometer" complete system Fraunhofer HHI has now found a way with a system that integrates all the components and processes required for its mobile, flexible real-world usage.

Developed by Fraunhofer HHI, the "TeraWave Time Domain Spectrometer" complete system packs all the components and processes needed (Photo: Fraunhofer HHI)

A new chip from Fraunhofer HHI tones up THz for real-world usage

The control unit of the complete systems contains telecom-developed lasers which emit ultra-short light pulses on what is known as the "Telecom wavelength" of 1.5 µm. This laser light is sent via flexible standard fiber optic cable to moveable THz emitter and detector heads. What is really crucial here are the Opto-Chips built into these THz heads.

Fraunhofer HHI THz sensor systems can be flexibly integrated into fabrication workflows

For realization of the complete system, Dr. Bernd Sartorius, group manager of Terahertz Technology at Fraunhofer HHI, and his team have integrated these chips in fiber-coupled flexible emitter and detector modules. As Bernd Sartorius explains, "Our system takes terahertz out of the lab environment. Our terahertz sensors can be flexibly integrated in a huge variety of fabrication and monitoring workflows. Control and evaluation is done by the laptop."

Terahertz at work

Monitoring the production and processing of plastics is one important area of use for terahertz sensors. In the food industry mobile complete systems can be used to scan packaging and foodstuffs to monitor the quality of contents. Unlike metal detectors, this system can even detect non-metallic materials like splinters of glass in chocolate.

The new technology is also ideal for the scanning of letters and packets to detect possible bio-weapons or explosives. The photo below shows a powder-filled plastic pouch between two sections of corrugated cardboard representing part of a packet. The THz emitter and detector heads developed by Fraunhofer HHI conduct a THz spectroscopic analysis of the powder. The THz transmission spectrum on the left shows an absorption band which identifies the powder as harmless lactose.