Ultrafast, multiphoton-pump, multiphoton-probe spectroscopy
Methods for pump-probe spectroscopy are provided. In an embodiment, such a method comprises directing pump light having a frequency ω pump at a location in a sample to excite a transition between two quantum states of a target entity in the sample, directing probe light at the location to generate a coherent output signal having a frequency ω output and a wavevector k output , and detecting the output signal as the probe light is scanned over a range of frequencies. In the method, either the transition excited by the pump light is a multiphoton transition corresponding to a frequency difference of n*ω pump , wherein n≥2; or the probe light is a set of m coherent light pulses, each coherent light pulse having a frequency ω m and a wavevector k m , wherein m≥2; or both. Systems for carrying out the methods are also provided.
1. A method for pump-probe spectroscopy, the method comprising:
(a) directing pump light having a frequency ω pump at a location in a sample to excite a transition between two quantum states of a target entity in the sample,
(b) directing probe light at the location to generate a coherent output signal having a frequency ω output and a wavevector k output ,
wherein the transition excited by the pump light is a multiphoton transition corresponding to a frequency difference of n*ω pump , wherein n≥2; or
wherein the probe light is a set of m coherent light pulses, each coherent light pulse having a frequency ω m and a wavevector k m , wherein m≥2; or
both; and
(c) detecting the output signal as the probe light is scanned over a range of frequencies.
2. The method of claim 1 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
3. The method of claim 1 , further comprising repeating steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeating steps (a)-(c) at one or more different values of ω pump or both.
4. The method of claim 1 , wherein the transition excited by the pump light is the multiphoton transition corresponding to the frequency difference of n*ω pump , wherein n≥2,
wherein the probe light is a single coherent light pulse having a frequency ω probe and a wavevector k probe ,
and wherein ω output =−ω probe and k output =−k probe .
5. The method of claim 4 , wherein n=2, such that the transition excited by the pump light is a two-photon transition corresponding to the frequency difference of 2*ω pump .
6. The method of claim 5 , further comprising repeating steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeating steps (a)-(c) at one or more different values of ω pump or both.
7. The method of claim 1 , wherein the transition excited by the pump light is a single-photon transition corresponding to a frequency difference of ω pump ,
wherein the probe light comprises the m coherent light pulses, each coherent light pulse having the frequency ω m and the wavevector k m , wherein m≥2,
and wherein ω output =Σ±ω m and k output =Σ±k m .
8. The method of claim 7 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
9. The method of claim 7 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
10. The method of claim 9 , wherein ω output =ω 1 +ω 2 +ω 3 and k output =k 1 +k 2 +k 3 .
11. The method of claim 9 , further comprising repeating steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeating steps (a)-(c) at one or more different values of ω pump or both.
12. The method of claim 1 , wherein the transition excited by the pump light is the multiphoton transition corresponding to the frequency difference of n*ω pump , wherein n≥2,
wherein the probe light comprises the m coherent light pulses, each coherent light pulse having the frequency ω m and the wavevector k m , wherein m≥2,
and wherein ω output =+ω m and k output =Σ±k m .
13. The method of claim 12 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
14. The method of claim 12 , wherein n=2, such that the transition excited by the pump light is a two-photon transition corresponding to the frequency difference of 2*ω pump .
15. The method of claim 12 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
16. The method of claim 14 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
17. The method of claim 16 , wherein ω output =ω 1 +ω 2 +ω 3 and k output =k 1 +k 2 +k 3 .
18. The method of claim 16 , further comprising repeating steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeating steps (a)-(c) at one or more different values of ω pump or both.
19. A system for pump-probe spectroscopy, the system comprising:
optics configured to direct pump light having a frequency ω pump at a location in a sample and to direct probe light at the location;
a stage configured to support the sample;
a detector positioned to detect an output signal; and
a controller comprising a processor and a computer-readable medium operably coupled to the processor, the computer-readable medium having computer-readable instructions stored thereon that, when executed by the processor cause the system to
(a) illuminate the location with the pump light having the frequency ω pump to excite a transition between two quantum states of a target entity in the sample,
(b) illuminate the location with the probe light to generate a coherent output signal having a frequency ω output and a wavevector k output ,
wherein the transition excited by the pump light is a multiphoton transition corresponding to a frequency difference of n*ω pump , wherein n≥2; or
wherein the probe light is a set of m coherent light pulses, each coherent light pulse having a frequency ω m and a wavevector k m , wherein m≥2; or
both; and
(c) collect the detected the output signal as the probe light is scanned over a range of frequencies.
20. The system of claim 19 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
21. The system of claim 19 , wherein the computer-readable instructions, when executed by the processor cause the system to repeat steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeat steps (a)-(c) at one or more different values of ω pump or both.
22. The system of claim 19 , wherein the transition excited by the pump light is the multiphoton transition corresponding to the frequency difference of n*ω pump , wherein n≥ 2 ,
wherein the probe light is a single coherent light pulse having a frequency ω pump and a wavevector k probe ,
and wherein ω output =—ω probe and k output =—k probe .
23. The system of claim 22 , wherein n=2, such that the transition excited by the pump light is a two-photon transition corresponding to the frequency difference of 2*ω pump .
24. The system of claim 23 , wherein the computer-readable instructions, when executed by the processor cause the system to repeat steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeat steps (a)-(c) at one or more different values of ω pump or both.
25. The system of claim 19 , wherein the transition excited by the pump light is a single-photon transition corresponding to a frequency difference of ω pump ,
wherein the probe light comprises the m coherent light pulses, each coherent light pulse having the frequency ω m and the wavevector k m , wherein m ≥2,
and wherein ω output =Υ±ω m and k output =Σ±k m .
26. The system of claim 25 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
27. The system of claim 25 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
28. The system of claim 27 , wherein ω output =ω 1 +ω 2 +ω 3 and k output =k 1 +k 2 +k 3 .
29. The system of claim 27 , wherein the computer-readable instructions, when executed by the processor cause the system to repeat steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeat steps (a)-(c) at one or more different values of ω pump or both.
30. The system of claim 19 , wherein the transition excited by the pump light is the multiphoton transition corresponding to the frequency difference of n*ω pump , wherein n≥2,
wherein the probe light comprises the m coherent light pulses, each coherent light pulse having the frequency ω m and the wavevector k m , wherein m≥2,
and wherein ω output =Υ±ω m and k output =Υ±k m .
31. The system of claim 30 , wherein at least two of the coherent light pulses in the set of m coherent light pulses have different frequencies.
32. The system of claim 30 , wherein n=2, such that the transition excited by the pump light is a two-photon transition corresponding to the frequency difference of 2*ω pump .
33. The system of claim 30 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
34. The system of claim 32 , wherein m=3 and ω output =±ω 1 ±ω 2 ±ω 3 and k output =±k 1 ±k 2 ±k 3 .
35. The system of claim 34 , wherein ω output =ω 1 +ω 2 +ω 3 and k output =k 1 +k 2 +k 3 .
36. The system of claim 34 , wherein the computer-readable instructions, when executed by the processor cause the system to repeat steps (a)-(c) at one or more different time delay T values between the pump light and the probe light or repeat steps (a)-(c) at one or more different values of ω pump or both.