High power high efficiency fiber laser and method for optimizing wall plug efficiency thereof

Patent metadata

Field	Value
Publication number	US-10615570-B2
Application number	US-201414558339-A
Country	US
Kind code	B2
Filing date	Dec 2, 2014
Priority date	Dec 2, 2013
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

The inventive laser is configured with a plurality of pigtailed multimode (MM) diode lasers each receiving a direct input current at a room temperature which is maintained to be within a 20-25° C. inside the housing of the laser. The diode lasers each are configured to operate at a desired wavelength in an optimal operational range, in which the diode laser operates with a WPE range between 63% and 75%. The direct current inputted in each diode laser is selected to be below a threshold at an efficiency curve of the diode laser after which the efficiency of the diode laser starts decreasing while an output power of the diode laser continues to increase. The laser is further configured with a fiber gain block having an active fiber medium which is pumped with the cumulative pump output and operative to emit a laser output in a power range between hundreds of watts and tens and even hundreds of kilowatts at the desired wavelength in an optimal operation range. The optimal operational ranges of respective MM diode lasers and fiber gain block are matched to achieve a superposition of respective efficiency maximums providing an overall maximum system efficiency up to 55%.

First claim

The invention claimed is:

1. A high wall plug efficiency (WPE) fiber laser, comprising:
a plurality of pigtailed multimode (MM) diode lasers each receiving a direct input current at a room temperature and operative to emit respective outputs which are coupled together in a cumulative pump output, the diode lasers each being configured to operate at a pumping wavelength in an optimal operational range, in which the diode laser operates with a WPE range between 63% and 75%, wherein an efficiency curve that characterizes the laser diode has a maximum WPE value after which the efficiency of the diode laser starts decreasing while an output power of the diode laser continues to increase, the received direct input current is below a direct input current at the maximum WPE value of the efficiency curve; and
a fiber gain block having a gain medium pumped with the cumulative pump output and operative to emit a laser output in a power range between hundreds of watts and tens of kilowatts at a desired wavelength in an optimal operation range in which an optical to optical efficiency ranges between 80% and 90%,
wherein a cumulative contribution of the optimal operational ranges of respective MM diode lasers and fiber gain block achieve a superposition of respective efficiency maximums providing an overall maximum system efficiency up to 55%.

2. The high WPE fibre laser of claim 1 , wherein the gain medium is doped with ytterbium (Yb) ions, the maximum system efficiency of the fibre laser with the Yb gain block ranging between 45% and 55%.

3. The high WPE fiber laser of claim 1 , wherein the laser diodes each operate in the 63%-75% efficiency range at the room temperature range varying between 20 and 25° C.

4. The high WPE fiber laser of claim 1 further comprising a driver unit including a plurality of digital components which are connected to one another to output the current signal coupled into inputs of respective diode lasers, the driver unit being configured to operate in an optimal efficiency range with a 98% efficiency maximum which is superpositioned with the respective maximum efficiencies of the diode lasers and fiber gain block to provide the maximum system efficiency at the desired wavelength.

5. The high WPE fiber laser of claim 4 further comprising a power supply block energizing the driver unit and including a plurality of digital components which are configured to provide an operation of the power supply block in an optimal efficiency range with an efficiency maximum of about 95% which, when superpositioned with the respective maximum efficiencies of the diode lasers, power block and driver, provides the maximum system efficiency.

6. The high WPE fiber laser of claim 1 , wherein the fiber gain block is configured with an active fiber doped with ions of rare earth elements, the active fiber having a core selected from a single mode core or multimode core, wherein the core is configured to emit the laser output in a single mode.

7. The high WPE fiber laser of claim 6 further comprising a delivery fiber directly coupled to an output of the fiber gain block, and guiding the laser output in the SM to a destination point, the delivery fiber being configured to have losses less than 0.1% at the desired wavelength to provide the maximum system efficiency.

8. The high WPE fiber laser of claim 6 further comprising a plurality of high WPE fiber lasers coupled in parallel to one another, each WPE fiber laser configured with the plurality of pigtailed MM diode lasers and the fiber gain block.

9. The high WPE fiber laser of claim 8 further comprising a delivery fiber, and a SM-MM fiber combiner which is coupled between the fiber gain block of respective WPE fiber lasers of the plurality of high WPE fiber lasers and the delivery fiber guiding the laser output to a destination point, wherein the SM-MM fiber combiner is configured to have less than a 2% loss and the delivery fiber is configured to have losses less than 0.1% at the desired wavelength to provide the maximum system efficiency.

10. The high WPE laser of claim 1 further comprising an additional fiber gain block coupled in series with an input of the fiber gain block in a master oscillator/power amplifier configuration (MOPA).

11. A method for optimizing wall plug efficiency (“WPE”) of a fiber laser, comprising:
generating a direct input current for a diode laser, the direct input current determined from an efficiency curve that characterizes the diode laser and has a maximum WPE value after which the efficiency of the diode laser starts decreasing while an output power of the diode laser continues to increase, the received direct input current is below a direct input current at the maximum WPE value of the efficiency curve;
coupling the direct current into each of pigtailed multimode (MM) diode lasers at a room temperature, thereby operating each diode laser at a pumping wavelength and in a WPE range between 63% and 75%;
coupling together outputs of respective MM diode lasers in a cumulative pump output;
inputting the cumulative pump output into a gain medium of a fiber gain block, thereby emitting a laser output in a power range between hundreds of watts and tens of kilowatts at a desired wavelength in an optimal operational range in which an optical to optical efficiency of the fiber gain block ranges between 80% and 90%,
wherein a cumulative contribution of the optimal operational ranges of respective MM diode lasers and fiber gain block achieve a superposition of respective efficiency maximums providing an overall maximum system efficiency of up to 55%.

12. The method of claim 11 , wherein the gain medium is ions of ytterbium (Yb), the WPE of the fiber laser with the Yb gain block ranging between 45 and 55%.

Assignees

• Ipg Photonics Corp

Inventors

• Gapontsev Valentin
• Fomin Valentin
• Scherbakov Eugene
• Ovtchinnikov Alex
• Ferin Anton
• Abramov Andrey

Classifications

• H01S3/1618

  ytterbium · CPC title

• H01S5/4012

  Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms · CPC title

• H01S3/2308

  Amplifier arrangements, e.g. MOPA · CPC title

• H01S5/065 Primary

  Mode locking; Mode suppression; Mode selection {; Self pulsating} · CPC title

• H01S3/067

  Fibre lasers · CPC title