TY  - JOUR
A1  - Kurzke, Henning
A1  - Kiethe, Jan
A1  - Heuer, Axel
A1  - Jechow, Andreas
T1  - Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal
JF  - Laser physics letters
N2  - The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments.
KW  - nonlinear frequency conversion
KW  - periodically poled material
KW  - waveguides
KW  - incoherent radiation
Y1  - 2017
U6  - https://doi.org/10.1088/1612-202X/aa6889
SN  - 1612-2011
SN  - 1612-202X
VL  - 14
PB  - IOP Publ.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Jechow, Andreas
A1  - Seefeldt, Michael
A1  - Kurzke, Henning
A1  - Heuer, Axel
A1  - Menzel, Ralf
T1  - Enhanced two-photon excited fluorescence from imaging agents using true thermal light
JF  - Nature photonics
N2  - Two-photon excited fluorescence (TPEF) is a standard technique in modern microscopy(1), but is still affected by photodamage to the probe. It has been proposed that TPEF can be enhanced using entangled photons(2,3), but this has proven challenging. Recently, it was shown that some features of entangled photons can be mimicked with thermal light, which finds application in ghost imaging(4), subwavelength lithography(5) and metrology(6). Here, we use true thermal light from a superluminescent diode to demonstrate TPEF that is enhanced compared to coherent light, using two common fluorophores and luminescent quantum dots, which suit applications in imaging and microscopy. We find that the TPEF rate is directly proportional to the measured(7) degree of second-order coherence, as predicted by theory. Our results show that photon bunching in thermal light can be exploited in two-photon microscopy, with the photon statistic providing a new degree of freedom.
Y1  - 2013
U6  - https://doi.org/10.1038/NPHOTON.2013.271
SN  - 1749-4885
SN  - 1749-4893
VL  - 7
IS  - 12
SP  - 973
EP  - 976
PB  - Nature Publ. Group
CY  - London
ER  -