Stabilizing optical frequency combs
A method for operating a laser device ( 1 ), wherein an optical frequency comb can be stabilized and the frequencies of the modes thereof are describable by the formula f m =m×f rep +f 0 , where f rep is a mode spacing, f 0 is an offset frequency and m is a natural number. At least one signal (S 1 , S 2 , S 3 , S 4 ) is determined, which correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep of the frequency comb. The actual value of the degree of freedom (F) is set in a predetermined capture range (F) of a second control unit ( 40 ) using a first control unit ( 10 ) on the basis of the signal. As soon as the capture range (ΔF capture ) of the second control unit ( 40 ) is reached, the second control unit ( 40 ) is activated and the actual value is regulated to an intended value (ΔF intended ) with the aid of the second control unit ( 40 ).
1. A method for operating a laser device ( 1 ) comprising the steps:
a) providing an optical frequency comb having a plurality of modes, the frequencies of which are describable by the formula f m =m×f rep +f 0 , wherein m is a natural number, f rep is a mode spacing and f 0 is an offset frequency,
b) determining at least one signal (S 1 , S 2 , S 3 , S 4 ) that correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep ,
c) transmitting, to a first control unit ( 10 ), at least one first input signal, the at least one first input signal being included in a set of the at least one signal (S 1 , S 2 , S 3 , S 4 ),
d) adjusting, by the first control unit ( 10 ), the actual value of the degree of freedom (F) to a predetermined capture range (ΔF capture ) of a second control unit ( 40 ) on the basis of the at least one first input signal,
e) activating the second control unit ( 40 ), once the capture range (ΔF capture ) of the second control unit ( 40 ) is reached and,
f) controlling the actual value to a target value (F intended ) by means of the second control unit ( 40 ),
characterized in that the second control unit ( 40 ) comprises a single second control loop ( 42 ) or a group of cascaded second control loops ( 42 ) that control, on the basis of a single second input signal (S 4 ) included in the set of the at least one signal, one or more actuators ( 8 a , 8 b , 8 c , 8 d , 8 e ), wherein the second control loops ( 42 ) arranged downstream in the cascading are configured to keep respective second control loops ( 42 ) that are arranged upstream within their respective control ranges.
2. The method of claim 1 , characterized in that the first control unit ( 10 ) comprises a plurality of first control loops ( 12 ) that are sequentially used so as to bring the actual value of the degree of freedom (F) into the capture range (ΔF capture ) of the second control unit ( 40 ).
3. The method of claim 2 , characterized in that the sequential usage of the first control loops ( 12 ) is controlled by a state machine ( 30 ).
4. The method of claim 1 , characterized in that the second input signal is derived from a beat signal and the sign of the beat frequency is determined prior to or during the activation of the second control unit ( 40 ).
5. The method of claim 1 , characterized in that the at least one first input signal comprises the second input signal.
6. The method of claim 1 , characterized in that the first control unit ( 10 ) separately selectively activates one or more second control loops ( 42 ).
7. The method of claim 1 , characterized in that the first control unit ( 10 ) adjusts one or more of the actuators ( 8 ) controlled by the second control loops ( 42 ) in parallel or alternatively to the second control unit ( 40 ).
8. The method of claim 1 , characterized by driving one or more actuators ( 8 ), which are independent of the second control unit ( 40 ), by means of the first control unit ( 10 ).
9. The method of claim 1 , characterized in that the first control unit ( 10 ) processes at least one actuator signal that represents the control value of an actuator ( 8 ).
10. The method of claim 1 , characterized in that, when the actual value is outside a set validity range (ΔF validity ), the first control unit ( 10 ) varies a control value of at least one actuator ( 8 ) in a stochastic or uniform manner until the validity range (ΔF validity ) is reached again.
11. The method of claim 10 , characterized in that a verification determining whether the actual value is within the validity range (ΔF validity ) is performed by determining a power level of a beat signal.
12. The method of claim 1 , comprising the step of driving at least one actuator ( 8 ) depending on one or more previous states of the first control unit ( 10 ).
13. The method of claim 1 , characterized in that the offset frequency (f 0 ) and the mode spacing (f rep ) of the frequency comb are stabilized.
14. The method of claim 13 , characterized by detecting a state of successful stabilizing and then displaying or forwarding a message indicating the state of successful stabilizing.
15. The method of claim 13 , characterized by an algorithm for automatically returning to the stabilized operation, when the state of stabilizing has been left, in particular, by repeating the steps a) to f).
16. A method for operating a laser device ( 1 ) comprising the steps:
a) providing an optical frequency comb having a plurality of modes, the frequencies of which are describable by the formula f m =m×f rep +f 0 , wherein m is a natural number, f rep is a mode spacing and f 0 is an offset frequency,
b) determining at least one signal (S 1 , S 2 , S 3 , S 4 ) that correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep ,
c) transmitting, to a first control unit ( 10 ), at least one first input signal, the at least one first input signal being included in a set of the at least one signal (S 1 , S 2 , S 3 , S 4 ),
d) adjusting, by the first control unit ( 10 ), the actual value of the degree of freedom (F) to a predetermined capture range (ΔF capture ) of a second control unit ( 40 ) on the basis of the at least one first input signal,
e) activating the second control unit ( 40 ), once the capture range (ΔF capture ) of the second control unit ( 40 ) is reached and,
f) controlling the actual value to a target value (F intended ) by means of the second control unit ( 40 ),
characterized in that the first control unit ( 10 ) comprises a plurality of first control loops ( 12 ) that are sequentially used so as to bring the actual value of the degree of freedom (F) into the capture range (ΔF capture ) of the second control unit ( 40 ).
17. A method for operating a laser device ( 1 ) comprising the steps:
a) providing an optical frequency comb having a plurality of modes, the frequencies of which are describable by the formula f m =m×f rep +f 0 , wherein m is a natural number, f rep is a mode spacing and f 0 is an offset frequency,
b) determining at least one signal (S 1 , S 2 , S 3 , S 4 ) that correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep ,
c) transmitting, to a first control unit ( 10 ), at least one first input signal, the at least one first input signal being included in a set of the at least one signal (S 1 , S 2 , S 3 , S 4 ),
d) adjusting, by the first control unit ( 10 ), the actual value of the degree of freedom (F) to a predetermined capture range (ΔF capture ) of a second control unit ( 40 ) on the basis of the at least one first input signal,
e) activating the second control unit ( 40 ), once the capture range (ΔF capture ) of the second control unit ( 40 ) is reached and,
f) controlling the actual value to a target value (F intended ) by means of the second control unit ( 40 ),
characterized by driving one or more actuators ( 8 ), which are independent of the second control unit ( 40 ), by means of the first control unit ( 10 ).
18. A method for operating a laser device ( 1 ) comprising the steps:
a) providing an optical frequency comb having a plurality of modes, the frequencies of which are describable by the formula f m =m×f rep +f 0 , wherein m is a natural number, f rep is a mode spacing and f 0 is an offset frequency,
b) determining at least one signal (S 1 , S 2 , S 3 , S 4 ) that correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep ,
c) transmitting, to a first control unit ( 10 ), at least one first input signal, the at least one first input signal being included in a set of the at least one signal (S 1 , S 2 , S 3 , S 4 ),
d) adjusting, by the first control unit ( 10 ), the actual value of the degree of freedom (F) to a predetermined capture range (ΔF capture ) of a second control unit ( 40 ) on the basis of the at least one first input signal,
e) activating the second control unit ( 40 ), once the capture range (ΔF capture ) of the second control unit ( 40 ) is reached and,
f) controlling the actual value to a target value (F intended ) by means of the second control unit ( 40 ),
characterized in that, when the actual value is outside a set validity range (ΔF validity ), the first control unit ( 10 ) varies a control value of at least one actuator ( 8 ) in a stochastic or uniform manner until the validity range (ΔF validity ) is reached again.
19. A method for operating a laser device ( 1 ) comprising the steps:
a) providing an optical frequency comb having a plurality of modes, the frequencies of which are describable by the formula f m =m×f rep +f 0 , wherein m is a natural number, f rep is a mode spacing and f 0 is an offset frequency,
b) determining at least one signal (S 1 , S 2 , S 3 , S 4 ) that correlates with an actual value of a degree of freedom (F), wherein the degree of freedom (F) is a linear combination of the offset frequency f 0 and the mode spacing f rep ,
c) transmitting, to a first control unit ( 10 ), at least one first input signal, the at least one first input signal being included in a set of the at least one signal (S 1 , S 2 , S 3 , S 4 ),
d) adjusting, by the first control unit ( 10 ), the actual value of the degree of freedom (F) to a predetermined capture range (ΔF capture ) of a second control unit ( 40 ) on the basis of the at least one first input signal,
e) activating the second control unit ( 40 ), once the capture range (ΔF capture ) of the second control unit ( 40 ) is reached and,
f) controlling the actual value to a target value (F intended ) by means of the second control unit ( 40 ),
wherein when the actual value is outside a set validity range, the first control unit drives at least one actuator depending on one or more previous states of the first control unit.
20. The method of claim 17 , characterized in that the first control unit ( 10 ) processes at least one actuator signal that represents the control value o an actuator ( 8 ).
21. The method of claim 18 , comprising at least one actuator ( 8 ) that is driven depending on one or more previous states of the first control unit ( 10 ).