Laser ignition system

Patent metadata

Field	Value
Publication number	US-9698560-B2
Application number	US-201415030538-A
Country	US
Kind code	B2
Filing date	Aug 25, 2014
Priority date	Oct 23, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A laser ignition system, in particular for an internal combustion engine, including a vertical emitter and a laser-active crystal, the laser-active crystal being doped in at least some areas using ytterbium, the ytterbium-doped area having a length of 200 μm to 7000 μm. The monolithic laser is based on a YAG or LuAG host crystal having 3 differently doped areas: a laser-active ytterbium-doped area, an undoped area which determines the resonator length and therefore the pulse duration, and a chromium-doped or vanadium-doped area for the passive Q-switch. The resonator is delimited by 2 mirrors.

First claim

What is claimed is:

1. A laser ignition system for an internal combustion engine, comprising:
a vertical emitter used as a pump light source; and
a laser-active crystal having three areas, the laser-active crystal being doped in at least some of the three areas using ytterbium;
wherein the laser-active crystal is at least in areas at least one of: i) a YAG host crystal, ii) a LuAG host crystal, iii) a GGG host crystal, and iv) a GSGG host crystal,
wherein a first area is an ytterbium-doped area,
wherein a second area of the laser-active crystal is essentially undoped,
wherein a third area of the laser-active crystal is doped using chromium (Cr 4+ ) or vanadium (V 3+ ),
wherein the area which is doped using ytterbium has an ytterbium doping of 3 at % to 30 at %,
wherein the third area is a passive Q-switch and has an initial transmission of not less than 30% for the wavelength generated in the laser-active material,
wherein the vertical emitter is able to emit a wavelength in a range from at least one of: i) 935 nm to 940 nm, and ii) 965 nm to 985 nm,
wherein the laser ignition system has a resonator which is delimited by a first resonator mirror and a second resonator mirror,
wherein the first resonator mirror is located in the form of a coating on a front end of the laser-active crystal facing toward the pump light source,
wherein the second resonator mirror is located as a coating on a front end of the laser-active crystal facing away from the pump light source,
wherein the first area has a length in the range of about 200 μm to about 7000 μm,
wherein the second area has a length in the range of about 4 mm to about 49 mm,
wherein the third area has a length in the range of about 50 μm to about 150 μm,
wherein the laser-active crystal, excluding the first resonator mirror and the second resonator mirror, has a total length of 5 mm to 50 mm, and
wherein the Yb-doping concentration is selected to be sufficiently high so that the absorption length of the pump light source is 200 μm to about 7000 μm long and corresponds to approximately half of a Rayleigh length of the pump light source.

2. The laser ignition system as recited in claim 1 , wherein the ytterbium-doped area has a length of 300 μm to 5000 μm.

3. The laser ignition system as recited in claim 1 , wherein at least three areas of the laser-active crystal have the same host crystal.

4. The laser ignition system as recited in claim 1 , wherein the third area has a length of greater than 100 μm.

5. The laser ignition system as recited in claim 1 , wherein the laser ignition system is configured as a laser spark plug having at least one of an electrical line, an optical line, and a thermal line.

6. The laser ignition system as recited in claim 1 , wherein the laser ignition system is configured as a laser spark plug having at least one of: i) an arrangement for installation on an internal combustion engine, and ii) an arrangement for optical imaging of an emitted laser beam into a combustion chamber of an internal combustion engine.

7. The laser ignition system as recited in claim 1 , wherein the laser ignition system is configured as a laser spark plug having a line for a cooling liquid for cooling at least one of the pump light source and the laser active crystal.

Assignees

• Bosch Gmbh Robert

Inventors

• Ridderbusch Heiko

Classifications

• H01S3/094084

  with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators · CPC title

• H01S3/1618

  ytterbium · CPC title

• F02P23/04 Primary

  Other physical ignition means, e.g. using laser rays · CPC title

• H01S3/09415

  the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping · CPC title

• H01S3/0627

  the resonator being monolithic, e.g. microlaser · CPC title