~8

StarTiger "under skin" feature

7he development of the 5tarTige,, 'co/our' terahet tz imager, mtegratps planar antenna, pl~nar detector; micro ma(hining, photomc band gap mater/a/,, and min~atunsed back end electronics technologie,, One of the team members a/ign5 the scanning mechanism of the first prototvp~

A special R&I) [cam has t:lken

just m(mths to achieve a signifi-

Callt advallCC in lc raher tz inlag-

ing technolog) . The StarTigcr

project, f lmdcd by the ESA

(European Space Agenc~ ) galh-

ered researchers fl 'om Enrope

at the CCLRC Rutherford

Apple ton Laboratory (RAL).Thc

work has led to t echno logy

firsts and pa ten t applications.

ESA wan ted to investigate tera-

h e r t z imaging in space research

anti tilt: StarTiger concep t of

carrying Otll the rcscarch.

Ainted at rapkt n e w t echnoh)gy

devclolmlent , StarTiger was

aligned wi th tile Agency 's inno-

vation polic).

Tcmher tz radiation occup ies

the s p e c t r u m b e t w e e n infrared

and microwave regions. Space

appl icat ions present ly include

astronomy, a tmos l lhcre physics,

car lh and env i ronmen t ITlOni-

tor ing as well as medical imag-

ing and securi ty sys tems.

The StarTiger team d e m o n s t r a t -

e d its first passive teraher tz

image of a hand, less than threc

m o n t h s into the four -month

project.

Micro-lhbricated teraher tz

de tec to r s and all advanced

imaging sys tem incorpora t ing a

two-coh)ur 16-pixel arra~ the

size of a pos tage s t amp were

incorpora ted with silicon

MEMs. "File sys tcm images con-

firm the mys ter ious na ture of

lcraher tz waves unexpec ted ly

showing details o f ' u n d e r skin'

li:atures.

Access t() 1st class facilities, the

opport tul i ty to fOCUS O11 tasks

with minimal distract ions :md

administrat ive overheads s eems

to prove the StarTigcr concept .

Oxygen molecule envisioning TEM

J i --

• , w o i i i

0 0 0 Sr @ OeOoOe

o G O @ O o O o O e

° o @ 0 @

©111]'~

(a) (b) (c) (d)

Strontium t~tanate ~5~ 770,) in tlve electron microscope The structure (a, 5r -

st;ontium, h - htan/um, 0 - oxygen) b imaged with a "cldssica/" electron microscope ;b) and n~ ( ompanson w~th the corrected microscope (c) in a simulation Where pre_vious/v only the heavy strontium atoms were dis- cernible (b), the/ightel oxygen atoms are now also directly visible (c) The scientist5 car, even identify oxygen v~cancie~ (d,

Scientists fl'om Research

( icnlrc Jfilich. the I~m'opcan

Molecular Biolog) l ,ahoralorx

in Hcidclber~ and l)armstadt

I Jniversity of~J~,chnologx have

made individual oxygen a toms

visihle with a rEx4 (m per

ovski tes mater ia ls

A techn ique has hccn dove[

oped 1o c()rrccl the aberrat ions

in the mic roscope wh ich leads

to bhwrcd images in wh ich no

individtlal oxygen atonls can bt"

seen. Ceramic materials on tile

basis of oxides with perovski tc

s t ruc ture - including hariunl

and s t ront innl titaniltC - plity a

major role in nlodern electron-

ics. Pcrovskitcs are also the

base material fi)r high-tcmpcr:l-

tnre s tq)erconductors , increas-

ingly needed in ultrathin films.

A major p rob lem is the correc t

ad jus tment of oxygen con ten t

wh ich critically de t e rmines the

electrical p roper t i e s .The

absence ()f it [(*x'~.- oxygen a toms

in tile electrically active TF

zones would intpair its func t ion

says ProE Knut [ !rban from the

Jfilich Inst i tute of Solid State

Research.TEM can check this

a tomic precis ion but distorted

images mean no individual oxy-

gen a toms can be recogniscd.

Now abcrra t ion-c( l r rcctcd 'TEM

with a specially shaped magnet-

it; lens, pe rmi t s oxygen to be

imaged atomical l ) for thc first

t ime, enabl ing oxygen con t en t

to bc measu red quantitatively

i l l atomic d imens ions . 1Trban

( w h o worked with mic roscopy

specialist, l)r Markus Lcntzen

and materials scient is t Dr C h u n

l,in Jia) is conv inced that this

will replace the classical high-

resolution e lec t ron mic roscope

in many materials sc ience

fields.

ORCS carry the TORCH Finland's Optoe lec t ron ics

Research Centre (ORC) at

1ampe re University of Tech-

nology has won a two-~ear

C l . 0 8 m Nat ionaITectmoh)gy

Agency grant t() fund develop-

men t of high-intensi ty ultn~-

shor t -pulse fibre lasers, tune-

able b roadband light enl i t tcrs

in optical fibre sys tems, and

dilute nitrkle lasers oscillating

at the wave leng th of 1.3mm.

Project TORCH (Towards

Lighter Technoh)gies) will

explore ways to achieve Dm-

tosecond- reg imc optical pu lses

in tegrated with senl iconductor ,

saturable ahsorbe r mirrors, and

deveh)p GalnNAs edge emi t t ing

devices and VCSELs.

ProE Markus Pcssa, director <)f

()RC said the crystal g rowth

facilities includes five MBE sys-

t ems and an opto device ktbri-

cat ion area. A new ORC build-

ing is a lmost comp le t ed and

C1.4m fi_mded as 'cost share ' by

the El I, Pirkanmaa TE-Centrc

(Finland) and industry.

ORC has ach ieved r ecogn i t ion

fi)r its work in ( ;a lnAsN work

and des igned and fabr ica ted

edge-emi t t ing GalnAsN / (;aAs

(. luantum well lasers ope ra t i ng

at 1.321urn.The layer s t ruc tu re

is g r o w n by MBE. C o n t in u o u s -

wave ope ra t i on at low thresh-

old cu r r en t has b e e n d e m o n -

s t ra ted at r oom t empera tu re .

Over l O 0 m W light p o w e r in

pu l se m o d e and 4 0 m W in cw

m o d e have been achieved . For

an u n c o a t e d 1 .6mm long laser

hav ing a sha l low ridge s t r ipe

the t h r e s h o M cu r r en t d en s i t )

is S63 A/cm2. In 2002, ORC

d e m o n s t r a t e d a photo-

p u m p e d 1.28Bin c o n t i m u m s -

wave vert ical-cavity surface-

emi t t i ng laser g r o w n in a sin-

gle nuc l ea t i on p r o c e s s by

MBE.

I I I -Vs REVIEW VOL 16 - NO 2 - M A R C H 2 0 0 3