BEGIN:VCALENDAR
VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:69d8db9bd82ef
DTSTART:20220131T140000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20220131T170000Z
LOCATION:Auditorium and Online (Teams)
SUMMARY:ICFO | SEBASTIÁN CASTILLA GÓMEZ
CLASS:PUBLIC
DESCRIPTION:Long wavelength light contains the infrared and terahertz (THz)
  spectral range of the spectrum. This wavelength range spans approximately
  from 1 &micro\;m to 1 mm. Several applications can be explored in this sp
 ectral range such as thermal imaging\, temperature monitoring\, night visi
 on\, etc. Moreover\, molecular vibrations resonate at these energies that 
 are the fingerprints for compounds identification via molecular spectrosco
 py. Also\, THz light has an important role in security since at these freq
 uencies is possible to achieve a higher resolution for imaging compared to
  millimeter waves that are typically used in airports. Despite all these p
 otential applications\, long wavelength light technology still remains non
 -fully exploited. One of the reasons is due to the lack of competing instr
 umentation such as sources\, modulators\, detectors\, sensors\, etc. In pa
 rticular\, regarding the detectors\, the commercially available technology
  present some issues such as the temperature of operation\, speed\, sensit
 ivity\, dynamic range\, broadband frequency operation\, CMOS compatibility
 \, size and compactness\, etc. The extensive research during the last year
 s on graphene and other 2D materials has opened new possibilities of novel
  light matter interactions that can unveil the next generation photodectec
 tors and sensors\, ascribed to the advantages respect to conventional semi
 conductors.In this thesis\, we focus on developing novel photodetection pl
 atforms in the mid\, longwave infrared and THz range based on graphene pn-
 junctions with integrated metallic nanostructures and hyperbolic 2D materi
 al. We have successfully integrated an antenna with a graphene pn-junction
  for highly sensitive and fast THz detection in this regime. This novel te
 rahertz detector exploits efficiently the photothermoelectric (PTE) effect
 \, based on a design that employs a dual-gated\, dipolar antenna with a na
 nogap. We have demonstrated that this novel detector leads to an excellent
  performance\, which fulfills a combination of figure-of-merits that is cu
 rrently missing in the state-of-the-art detectors. We also overcame the ma
 in challenge of infrared photodetectors\, which is to funnel the light int
 o a small nanoscale active area and efficiently convert it into an electri
 cal signal. We achieve this by efficient coupling of a plasmonic antenna t
 o hyperbolic phonon-polaritons in hBN to highly concentrate mid-infrared l
 ight into a graphene pn-junction. We use a metallic bowtie antenna and H-s
 hape resonant gates that besides concentrating the light into its nanogap\
 , their plasmonic resonances spectrally overlap within the upper reststrah
 len band (RB) of hBN (6-7 &mu\;m)\, thus launching efficiently these HPPs 
 and guiding them with constructive interferences towards the photodetector
  active area. Additionally\, by having two different antennas orientation\
 , it allows us to have sensitive detection in two incident polarizations. 
 Furthermore\, we have shown mid and long-wave infrared photocurrent spectr
 oscopy via electrical detection of graphene plasmons\, hyperbolic phonon-p
 olaritons and their hybridized modes. We combined in one single platform t
 he efficiently excited polaritonic material that also acts as a detector i
 tself. We identified peaks in the photocurrent spectra that evolves and bl
 ue shift by increasing the gate voltage\, which are related to the polarit
 onic resonances. Finally\, we investigated the electrical detection of mol
 ecular vibrations coupled to hyperbolic phonon polaritons in hBN. We detec
 ted this strong light-matter interaction via a graphene pn-junction placed
  at the vicinity of the molecules-hBN stack. The edges of the gap of the l
 ocal gates launch efficiently the hBN HPPs that interact with the CBP mole
 cular resonances that are spectrally located at the upper RB. We explored 
 this interaction as a function of the thickness of the molecular layers\, 
 near and far field contribution\, etc.
DTSTAMP:20260410T111435Z
END:VEVENT
END:VCALENDAR